solar panel

This afternoon my son and I fitted a 100w solar panel, before we connected it to the sergent ec328 we checked and were getting 21 readout on the multi meter. we then connected to the sergent and the best reading we could get is 12.4/12.5. is this right, or should I expect more, cheers.

If your batteries were already fully charged then maybe that's all you get. I'm sure someone else with have the answer.

The PANEL voltage is, in your case 21v, more or less a common panel voltage.
The solar converter reduces that to 14 or so volts to charge the batteries.
Assuming dark and no solar input a full nominal 12v battery should be 12.7 V.
Yours may not yet be full, see what they're like tomorrow evening without being used at all tomorrow

Near dusk here now, panel V is 15.9 reducing, clearly zero output. Starter battery is 13.5 and will reduce to its normal 12.7overnight. Leisure is 12.6 as it is in use right now. It'll drop to, perhaps 12.4 or so then get charged to full again by lunchtime tomorrow

Finally, it is always best to bypass anything with Sargent written on it. Get a dual battery controller from Photonic universe and connect from that direct to batteries. That's what we have and always have had on previous vans.....

The solar controller that's built into a Sargent EC328 is almost ~exactly~ the same dual-channel controller that Photonic Universe supply. Trying to bypass a Sargent EC328 will have almost no beneficial effect at all - in relative terms, it's a very efficient system compared to the EC500 and EC700.

As Paul says, what voltage you will see at the battery depends on the state of charge of the battery, and the amount of light falling on the panel - but you don't say what time of day the test was done.

It was around 3pm and mostly overcast, so it sounds like a good result, thanks all for your replies.

Ok - the critical time will be when you first get some proper sun on it. At that point (assuming the batteries are not already fully charged) you should see around 14.4V at the leisure battery, though as Ian says, anything above 14 should indicate that it's working OK. If the battery is already in a good state of charge, you should see it drop back to float mode, which will probably be towards the upper end between 13 and 14V.

As said you really need to run a full test, including exposure to good sun, and you need to be sure that the batteries are in good overall condition, but you should really be seeing a charging voltage at the battery terminals in the high 13’s at least. The resting voltage is a different matter and can only be measured in darkness, or with the panels isolated or covered.

My solar experience is recent and only with my own van, and I cannot comment on relative charge controller efficiencies, and I would not wish to appear to contradict those with greater experience in the field, but when I upgraded my solar recently (new panels, new controller, fat cables direct to batteries) the most obvious issue was undersized wiring from the panel to the controller, and more importantly from the controller to the batteries, via the Sargent EC700 and the various harness plug connections. In any 12 volt system voltage drop is the key issue and generous wiring sizing (hence minimal voltage drop) is vital to an efficient system. By far the most efficient system (as Ian intimates) is with the solar panels and controller wired directly to the batteries by the shortest possible route and with the fewest possible connections.

In weak sun this morning I am seeing 14.1 volts at my batteries.

I am afraid that undersize wiring is very evident throughout the Sargent wiring that was installed in my van, compounded by excessive cable run lengths, loops of excess harness and too many connections etc. I suspect that excess voltage drops are behind many of the electrical issues with these vans, including perhaps some of the water pump issues (not enough oomph at the pump to blow out the air locks?)

My advice is to ditch the built in charger which is a PWM chager and change it for either a Victron or Votronic MPPT charger.
The advantage of a MPPT controller is that it is a lot more efficient at extracting maximum solar power to convert to usable electricity than a PWM.
The advantage of Victron is that you get a nice bluetooth app for your smartphone so you can see at a glance how much or little your panel is producing plus a history going back at least 30 days.
I've got a 100w panel and a Victron SmartSolar MPPT 75/15 which fits exactly where the old solar charger in the 328s sits. I've also added a Vanbitz battery master which automatically keeps the engine battery topped up all year. The last part also works well over winter for me even with mainly cloudy days.
Both units sit nicely inside the 328s.

brianmor wrote:My advice is to ditch the built in charger which is a PWM chager and change it for either a Victron or Votronic MPPT charger.
The advantage of a MPPT controller is that it is a lot more efficient at extracting maximum solar power to convert to usable electricity than a PWM.
The advantage of Victron is that you get a nice bluetooth app for your smartphone so you can see at a glance how much or little your panel is producing plus a history going back at least 30 days.
I've got a 100w panel and a Victron SmartSolar MPPT 75/15 which fits exactly where the old solar charger in the 328s sits. I've also added a Vanbitz battery master which automatically keeps the engine battery topped up all year. The last part also works well over winter for me even with mainly cloudy days.
Both units sit nicely inside the 328s.

And I would reiterate, wire the new controller direct to your LB with nice fat wires.

I’m not a great one for apps but the Victron one is a very nice touch!

Mppt V Pwm.
Try this for a small discussion.

I have, as most may know, my 5th MH installation, of a 100 to 130w panel , a dual battery Pwm controller connected directly to each battery via inline fuses. I also have a remote display so can monitor the whole system at any time.

Our loads are typical, led lighting, for now, 3 way fridge, TV, charging phones and tablets. We rarely use sites, and even then may not use EHU.

Typically our full battery voltage after solar is 12.8, lowest ever in morning pre solar 12.4 or 12.5.

In , shall we say, average weather the solar output to the batteries is zero by circa noon.

My point is this. Sure. I could get more output with Mppt, so my batteries would be full earlier, perhaps an hour or so, but then, like others, the solar then does nothing for the rest of the day?

So for less expense ( considerably) and the ease of getting a dual battery system which has been reliable over 5 vans now, where, really is the big advantage of Mppt????

This should make a change from eternal tyre pressures!!!!

If it works for you then of course I won't knock it, but for oddballs like me who prefer to boil an electric kettle rather than fill the van with gas fumes, and likes to cook with an air fryer etc. etc. and uses the van year round then I need a solar system that squeezes as much as possible out of what sun we get, particularly out of season, and harvests the maximum amps out of the limited area of solar panels that can be fitted. So far (with my new installation) the solar is still shoving a bit of charge in at dusk, but that may change a bit now the sun is out.