Solar Charger Wiring Advice

[brasdall]

Hi Folks,

 

I have a Dodge day van and have recently fitted a solar panel to trickle charge the starter and leisure batteries via a dual charge controller.

 

Please refer to the attached wiring schematic to give you an idea of the setup and equipment involved.

 

I have had 2 controllers and both have failed when I believe the lights have been turned on, the first controller (rated at 10A) burnt out on the leisure battery when running the internal lights but the starter battery stayed ok, the second (rated at 16A) failed completely.

 

I would appreciate any advice on the wiring arrangements and if I need a specific charge controller to achieve what I intend. I cant see why the controllers cannot handle this setup, unless I an doing something patently wrong, or is there likely to be a short...but if this was the case are the controllers not protected?

 

Thanks

Ben

[weldted]

I would separate the two earths at the solar panel controller, if you still have problems I would by a battery mate from Van-Bitz then just put the solar panel to only charge the leisure battery. The connect the battery mate it's only three wires one to leisure + one to leisure - one to engine battery - when the engine battery falls to one volt lower than the leisure battery it automatically starts a trickle charge from lb to eb. I have had this system since 2008 just fit and forget. Hope this helps.

[brasdall]

Thanks for your reply. I originally had the negatives separated with the first solar charger and that blew too, I don't get it as the lights aren't pulling too many amps.

 

Looking at the van bitz web site I found the battery master http://www.vanbitz.com/product/battery-master/ I guess this is the one?

 

There doesn't seem to be much info on the website about load ratings and solar panel charge loads did you get an info with yours? If not ill give van bitz a call.

 

Cheers

[ian81]

....first thing I would do is add some fuses

....second tie all negatives to ground eliminate the diode unecessary as the kemo provides isolation between the two positives

....third get it working ok just charging the leisure battery

 

....happily using akemo to charge both leisure and starter without any battery / battery device.

[witzend]

Definitely fit fuses on positive both sides of controller

[aandncaravan]

Your isolator in the Starter Earth supply is less than ideal. Better in the Positive cable?.

 

Please don't use a Battery Master style of charging, it works, but the way you have designed it will be much, much more efficient. The Battery Master way of doing things was ok 10 years ago when the alternative was prohibitively expensive, but a Dual battery regulator is a cheaper and much more efficient way of charging the Habitation and Starter battery.

 

The Kemo M174, which I assume you are using, is not a great Regulator.

The Kemo data sheet shows a 16A fuse should be inserted between the Solar Panel and the regulator, this is very important for safety.

There should also be appropriate fuses, no bigger than 8amp max, at each battery positive connection.

 

Additionally, while the Kemo is rated at 16A that is in single battery mode, each 'side' will pass no more than 8amp max when used in dual mode.

Those are MAXIMUMs, the ideally running current should be no more than 75% the max. I would guess you are running the Kemo beyond it's limits, which are probably not as high as advertised, possibly no more than 5amps continuous?

 

I suggest you start with a quality, Motorhome specific regulator with a design rating at least 25% higher than you require. Maybe in your case, considering the issues you have suffered already, you should think about a 50% buffer?

 

Make sure it is a proper Motorhome regulator and not one that 'says' it can be used on a Motorhome.

Some 'Dual battery' regulators will 'independently' charge two batteries, usually at better than 50/50, but not in a sophisticated way.

A Motorhome requires a special variation on this. Under most circumstances you want 99.9% of the charge to go to the Habitation battery and little to the Starter battery as most Starter batteries will be suffering little drain when the van is being used.

 

In Winter in Storage, you will want it the other way around as the Habitation shouldn't be suffering any drain but the Starter battery might, as the vehicle alarm/immobiliser is more likely to have been activated.

 

Many Dual battery chargers can often split no better than 80%/20% as their optimum, way too much for your Starter and wasting 20% you can otherwise use at the Habitation battery.

 

If you buy a decent Motorhome specific regulator, you will harvest more current where you need it.

 

Buy a Power Meter, they are less than £15 and will show you exactly what you are Harvesting over a day/week in Amp hours, but will also tell you the current/voltage being passed to help with diagnostics.

 

See our Solar pages for more info on fusing, wiring, Location, battery masters, etc : http://www.aandncaravanservices.co.uk/solar-power.php

 

 

 

.

 

 

[Dr Dave]

With reference to your diagram.

1) With the battery isolator switch open there is no route for the negative of the batteries to complete the circuit to chassis they are effectively 'floating' this could cause the regulator to be passing current in the wrong direction via the resistance to chassis of the van electrics. as your lighting load is connected negative to the bodywork.(chassis)

2) Remove the diode as this is raising the reference voltage to negative by the forward voltage drop of the rectifier under load this will be over 0.6 Volt assuming it is a silicon diode. this severely limits charging current.

3) You need to ground both negative terminals on the batteries to the chassis without the diode.

4) Seriously consider fitting fuses in the battery positives and the input and outputs of the solar regulator.

Just as a footnote check that the input to the solar regulator IE: from the solar panel is not connected to chassis either by design or fault as this would also be a route through the regulator electronics to chassis (completing the circuit that the lack of grounded negative terminals of the batteries will cause.)

Dave

[brasdall]

Thanks all for your input.

 

I missed the fuses from the diagram which are as specified by Kemo (between the panel and charger) and also on the +ve to both batteries, I have changed the fuses to 10A and 5A to be safe. The reason why I had the isolator on the -ve is to act both as a immobiliser and also prevent unidentifiable battery drain when not in use for long periods (recommended by others). I have since changed the starter battery as the previous one was poo. I have removed the diode and am just focussing on the leisure batt operation for now, which seems to be operating ok. I will also look at changing the isolator to the +ve if this is likely to help prevent the issues, once I reconnect the starter battery to a new charge controller (as I only have one channel working on the controller).

 

In terms of motorhome controllers I have had a brief look and found the below which is within budget, any comments?:

 

http://leisurelines.net/solar-charge-regulator-240w-2137-p.asp

 

Cheers

[aandncaravan]

Your poor Starter battery may have been a factor in the failure of the Kemo?

 

If the Starter Motor is operated it will draw all the power it needs from the Starter battery.

If the battery is poor, there is potential for the Habitation area battery to 'help out', sometimes via paths that it's power shouldn't travel down.

It has been known for light duty 'Split Charge' relays to fail under conditions of a poor Starter battery, often while a jump start takes place of a poor Starter battery. Hence one of reasons to never 'jump start' a Motorhome.

 

Maybe the isolation in your regulator of the two batteries isn't as good as it should be and the habitation battery tracked across to feed the Starter blowing up the Kemo?

 

 

The CBE Solar Regulator in your link is a very good one. One of the few Solar regulators specifically designed for Motorhomes.

However, it is only a single battery regulator not one of the Dual battery devices that charge both Habitation and Starter batteries.