Question: too much solar for the EDL?

[NorthernSands]

Hi all.

Our new (to us) MH should be ready to be picked up next weekend, but with a France trip planned for the week after, I want to try and get solar sorted ASAP. Our old Hymer Camp 64 has a solar panel (unknown wattage but I'd imagine ~80-100w) and that's been mostly fine for us on a 110ah habitation battery, not charged by the engine. We have never used a lot of electrics and have always lived 'off-grid' and I'd like to continue to do that. However, the new MH (1996-7 Hymer E700) will require more power, so I'm looking at a larger panel initially, then perhaps another battery later in the year.

Anyway, my question is this: The EDL in the MH is likely to have a max charge current of 10 - 15 amps (I'm not sure which model it is yet). I'm looking at the LRM 1218 (or Votronic MPPT equivalent) solar controller. The LRM can take a 275w panel (~22-23amps). Given that we'd never see the max output of any panel, I don't want a 150w panel (who's max wattage would match the 10amp EDL) as the normal charge rate would be much lower than max. I want a larger one to ensure we get the most we can get, delivering as close to the EDL max as we can. However, a 250w / 275w panel has the potential to exceed the max charge rate of the EDL in the locale and climes that we'll be in. If this happens, is it going to break anything / blow a fuse, or will the solar controller 'dump' the excess, and if so, how (heat? I know the LRM has a fan)?

As a footnote, I'd like to mention that perusing these forums has been extremely helpful in helping me understand how to approach putting solar on the van and how to integrate it into the more modern controller system, rather than just hand it to an installer. Thank you!

 

[SandraL]

Without knowing which ebl? I do not know its current rating or facilities to know / display charge and discharge from battery.

You could limit the solar charge by putting a fuse between the solar panel and solar controller, thus protecting the ebl from excessive charge. If it blows you may not realise until you have a flat battery....
.
If you do not want or need the current measuring facilities of the ebl you could connect solar controller direct to the leisure battery.

As a satisfied user I would pick the votronic mppt and also get the temp compensator thingy, more useful in warmer climes to avoid over heating the battery and reducing batt life.
The solar controller will not dump excess power, it just takes the required power, if available, from the panel. When battery is full solar controller will stop taking power from the panel. Whilst charging hard, ie low battery and plenty of sun, the controller will get warm, hence the fan.

 

[Lenny HB]

Normally the solar on the EBL is fused at 15amps but it is permissible to increase this fuse to 20 amps.

 

[NorthernSands]

Thanks for the info.

I suspect it'll be a Schaudt Elektroblock EBL, though I'm not sure which model. The above door controller is marked as a Panel 105 (also a Schaudt, I think); analogue voltage gauges to the left, central digital clock / temp gauge, and analogue amp gauge on the right.

I would like to use the gauge to monitor charge / discharge rates. Both the LRM and Votronic also supply some charge to the starter battery, which appeals.

 

[NorthernSands]

The EBL is a Schaudt Elektroblock EBL 105-2 and the Solar charge fuse is rated at 10amps. I could replace this to something higher, but I don't know the potential capacity of the internals (without opening it up).

The EBL is sufficiently old that the starter battery cable adaptor that comes with the LRM1218 won't fit, so I'm happy enough going for the Votronic; it'll be cheaper and I believe the trickle charge is at the recommended 13.2v rather than 13.4v.

So, that just leaves the question of what happens if the solar charge current from the controller exceeds 10amps. I'm guessing it would eventually blow the EBL fuse!

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[autorouter]

The EBL 105-2 is an older type of EBL, built for the days when 100W of solar panel was as much as anyone could imagine. Similarly the charger and battery charge percentage were designed when 100 amp-hours of battery capacity was huge.

The EBL still does a good job of feeding your habitation electrics, but it's probably a good idea to bypass it when it comes to using over 200 watts of solar power. I'd go with SandraL's suggestion and connect the solar controller direct to the leisure battery. If you get a dual battery controller, you can connect the starter battery too, to give it a trickle charge.

The solar controller only takes the power it needs from the panel. If there's no load on a panel, the panel just stops producing electrical power, so nothing gets overloaded.

You could get a battery monitor to replace the monitor function of the EBL, so you can see the battery state of charge. These usually involve fitting a 'shunt' into the main battery negative wire, connected to a display panel. Look at a Nasa BM-1 or Victron BMV. Some of them have temperature monitoring, and Bluetooth so you can see it on an app on your phone.

 

[JockandRita]

NorthernSands, the set up that SandraL and autorouter have suggested, is the set up we have on our 99 Hymer.
I have 2 X traction batteries, 2 X 85w solar panels, 1 X Battery Manager, and the original EBL 105. The solar controller (pre fused) feeds direct to the leisure batteries, with the battery manager transferring any unwanted charge from the leisure batteries, over to the starter battery, by up to 4 x amps.

This all works a treat for us, but to cater for when there is very little solar power, we also have a Sterling Battery to Battery charger installed. We are off grid much more than on grid.

Good luck getting the right balance.

Cheers,

Jock.

 

[NorthernSands]

Thanks, all.

I'm not fussed about 20amps of charge, rather I'd like to maintain 10 odd amps, even in less than perfect conditions. During winter, in the UK, a ~250w panel will give better charge than a 150w one, if much lower than even 10amps. I guess another option is to have two smaller (~120w) panels, and disconnect one in Summer.

I'll order the regulator now, get the panel when the van arrives and I know what space I have, then try different connection methods. I might have a poke inside the EBL and make a judgement call on whether to up-rate the fuse. The EBL does support 25amps of draw on different circuits, so the solar input might too, though I may need to down-rate another circuit to ensure balance on the internal current. We don't use a huge amount, so that might be OK. If that doesn't look good we and can always plumb straight to the battery.

Thabks, again.

 

[Boringfrog]

I don't think a 275W panel will give you 23Amps.

 

[JockandRita]

The highest ever reading observed from our 2 x 85w panels has been 9.9A, in the height of summer at around 14.00hrs, with the sun directly above them.

Cheers,

Jock.

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