Turbo-charging Motorhome Electrics

wildebus

Full Member
Good stuff. I'd be tempted to put a shroud on that switch to stop it getting knocked on accidently though.
OK, As said, 'twas a good idea and had a few ways I thought might work.
first idea was a non-starter (but just a couple of minutes spent checking, so no probs)
next one was doable but a bit of a effort (hey, it's Sunday. Day of rest!)
third time's the charm as the saying goes (y)

Fitted the Switch into a 30mm fitting (same size as the generic USB and 12V sockets are) and fitted the set into the hole I had made (due to unusual foresight, I had actually and consiously made the switch hole to suit this size despite not needing it that large originally).
Then mounted the CBE plate on top, using a larger modified blanking plate to give access to the switch whilst keeping it from being knocked accidentally.
1609679671519.png

The surround over the switch above has a 30mm diameter hole. I think I'll do one with a 25mm hole and smooth the edge off to make it a bit prettier, but I think the concept should work. The photo below shows how the switch is now sunken down...
1609679882826.png


Thanks for the suggestion, Steve. :)
 

wildebus

Full Member
Final (final? who said that?) Step completed this evening :)

I have installed the EasyPlus which lets me use off-grid 240V (via Inverter) on just about every circuit except the Room Heater.
I added the WAS-201 Auto-selecting AC switch to allow additional control over the Boiler and Fridge circuits to avoid draining the battery too much.
Adding in the Countdown Timer increases the flexibility of this circuit to allow it to be always available or just for a limited time even when below the chosen battery charge level.

There is one more thing that needed sorting though....
The EasyPlus is configured in AES (Automatic Energy Saving) mode so the inverter is in sleep mode unless called on (and in that mode only uses around 2W). The downside of this is that if you want to use the inverter for a small load, it won't switch on to drive that device.
A resolution for that is installed some Assistants into the EasyPlus

Three Assistants - one (general flag) configured to disable the AES feature when active; one programmable relay to activate the general flag and the same again, but this time to deactivate the general flag. And the control signal is sent to the Temp Sense as that is the one and only control sensor on the EasyPlus/Multiplus 1600 (Bigger Multipluses have a couple of inputs for this kind of thing).
I can use the Temp Sense on my EasyPlus as I am monitoring the Battery Temp via another device (I am using the Cerbo, but other Victron GX units or a BMV could be used)
1609707637970.png

To control this Assistant, you can use an external mechanical switch or, as I am doing, a remote relay. I am using Relay 2 on the Cerbo to run the assistant and so to force the Inverter to be active when off-grid, I go into the Cerbo Control Panel and turn the relay on.
I might use a switch instead to make it easier. I could even install another Countdown Timer in the same manner as I am doing the Boiler/Fridge setup to ensure I don't forget to re-enable the AES.
 

wildebus

Full Member
Something I didn't show in this thread is any info showing how the B2B is working?
As mentioned, I have an Ablemail AMC-12-12-60 Charger, which is a 60A nominal multi-stage Battery-to-Battery charger. This is an interesting unit and internally is actually a pair of 30A Chargers that are essentially paralleled, but can be configured in different ways if you wanted to (you could have one come on a slightly higher input voltage say if you had an alternator which you didn't want to fully load initially as a possible example).
Mine is configured with both having the same profile - to turn on at the same voltage and to deliver 14.3V in Absorption mode to suit my specific batteries.
This is what the BMV is reporting just after the engine is started:
1613523510163.png




And just after turning off the engine.
1613523683069.png

I've got a current load of around 5.5A (there are some very inefficient lights in the Autotrail which I don't tend to use as you can imagine!).

So that is showing a net charge of a little under 68A coming in from the B2B. A couple of extra points about this ...
1) On my testing, the Ablemail chargers always seem to put out around 10% more current than the rated output. The 30A units always send out 33-34A and this 60A unit is keeping that tradition up. That extra 8A is nice to have (y)
2) This output is from just starting the engine and it is idling with no pressure on the accelerator. So if you needed a quick battery boost after say a heavy night, whilst running the engine is not the ideal way to do it, at least you don't need to be revving up to get a decent alternator output.
 
Last edited:

Markd

Full Member
Whilst an alternator may deliver 70A at tickover isn't there a distinct possibility that it will get pretty hot doing doing so at such low rpm?
I seem to remember seeing a video from Sterling Power warning of this.
 

wildebus

Full Member
Whilst an alternator may deliver 70A at tickover isn't there a distinct possibility that it will get pretty hot doing doing so at such low rpm?
I seem to remember seeing a video from Sterling Power warning of this.
I understand that modern alternators have temperature protection and will throttle down their output if they get overheated?
 

Markd

Full Member
Probably - that would be sensible.
The facility to push in 60A at tickover is really useful - personally I don't see the harm in using the engine.
Although having said that it's likely to be 'cold' which is sub optimal but it'll get the job done.
 

wildebus

Full Member
Not hooked up at the moment and the batteries are down to 60%. I might start up the engine and leave it running for a little while and zap the alternator with a IR thermometer every few minutes to see what it does :)

Of course, when I quoted the B2B current, that would have been output current. The input from the alternator would have been higher due to charger losses (15% would be typical?) plus potentially more as it might be boosting the voltage as well. And there's more ... It would also have been running the fridge if it switched to the 12V input (I think it did in fact), so that 68A-70A could have been more like 85A or more?
I'll be having the fridge off AES next time I turn on to "idle-charge".
 

SquirrellCook

Full Member
One thing that I did think was misleading was that due to pulley sizes the alternator generally runs at twice the speed of a low revving Diesel engine. Mind you Anita generally doesn’t get above 2000 rpm in her van. I also suspect that most alternators are better than 50% efficient. If it’s true Anita’s van is only supposed to charge when slowing down or braking. Unless the battery is particularly discharged.
 

Markd

Full Member
I agree about alternator gearing - at tickover an alternator will probably be doing a bit more than 1500 rpm.
But it will be well below the revs needed to be able to deliver anything near the rated capacity.

It'll be interesting to see what Wildebus' real life temperature readings are.
 

wildebus

Full Member
I agree about alternator gearing - at tickover an alternator will probably be doing a bit more than 1500 rpm.
But it will be well below the revs needed to be able to deliver anything near the rated capacity.

It'll be interesting to see what Wildebus' real life temperature readings are.
Ran the engine for a short time ....
Now a few comments before the info:
  1. The engine battery was down to 12.2V - so around 50% discharged, so the alternator will be recharging that as well as feeding the B2B.
  2. I am only monitoring NET current in the Leisure Electrics.
  3. Fridge is off.
  4. Turned off the Leisure Electrics in the van. In reality, this means there is still a draw of around 0.8A for various reasons.
So checked the alternator temp immediately after starting the engine, and again just before stopping. I only ran this for around 30 minutes as I didn't want to be wasting fuel basically.
1614439439775.png

Getting a fairly steady 50A out of the 60A B2B. Now I would take a stab and say this is not the full output of the B2B as the alternator is limited at idle speed and there is likely to be a reasonable current from it going into the Starter Battery.
50A is not bad though and I would have got 25Ah into the battery in this 35 minute period the engine was on. 25Ah is a handy boost of power when the battery is low.
 

Markd

Full Member
@wildebus Thanks for the report.
55⁰ is cool enough and net 50A from B2B does suggest alternator 'throttling'
So with a degree of caution turning off the fridge you're getting a decent boost in the leisure batteries that would be very useful in the 'wild' if solar not available.
 

Nabsim

Full Member
A little less than I would get in 35 minutes running my generator. I think it’s about 21/22 months old now and just before I left Charlie I checked what it has done. 452 hours so far so it does get used lol. Will be run much less now I have the two Victron chargers installed.
I know this is nothing to do with alternator charging but gives a different option if, like me, you don’t like to idle the engine 👍
 

wildebus

Full Member
A little less than I would get in 35 minutes running my generator. I think it’s about 21/22 months old now and just before I left Charlie I checked what it has done. 452 hours so far so it does get used lol. Will be run much less now I have the two Victron chargers installed.
I know this is nothing to do with alternator charging but gives a different option if, like me, you don’t like to idle the engine 👍
I am not a fan of doing what I just did either :) it was purely an experiment to see the impact and effectiveness to do that if 'caught short' one day.

How do you know the hours used? is there a usage clock on your generator? that's posh 🎩
 

Nabsim

Full Member
There is a display on the front Dave, tell output and rpm (I think) on one screen, toggle display and it tells you running hours. It’s an lcd display rather than mechanical counter type
 

Markd

Full Member
Generator is fine if you have the payload - alternator is there already a d B2B is only a kilo or so.
Maybe if you have a generator you can have one less battery and there's no payload hit?
 

Users who viewed this discussion (Total:0)

Top