I’ve got 2 x 115 leisure batteries in a van and am after a charger to keep them topped up.

Does the max battery capacity of the charger matter? I’m looking at a noco genius 5 which says max capacity is 120Ah, but if there’s 2 batteries in parallel it’ll just take twice as long to charge? If it has to be connected for a few days it’s not an issue.

I could get a 10A charger which is rated to 230Ah but they are quite a bit more expensive.

Thanks

Do you have split relay already fitted and this is just to top it up?

I’ve had the same leisure battery for 7 years and it’s only ever been charged via the relay. Never put a trickle charger on it and it’s been fine, even when the van hasn’t been used for ages during lockdown

Yeah it’s got a split relay but it’s often used for trips that don’t involve a lot of driving, and might have fridge running for a day or two, or diesel heater running at night so it’s just to top up if the split charge from driving isn’t enough.

Split charge via relay is a horrible way to charge your battery anyway.

Fwiw I’d put the 70 quid from the Noco towards a 100w solar panel set up.

Then it’ll keep it’s self right automatically…

My split charge relay back up broke 3 years ago, I unplugged it. Don’t miss it.

How much will a solar panel top up in winter, I mean what sort of amp output would you get on a grey winter day?

Not got any numbers but Enough I don’t have to fart about sticking it on mains hook up to charge em. Battery’s remain fully charged when ever I go to use my van and as I said I don’t have a split charge any more.

That said if I was going for a week away in December to sit in my van all day it might concern me more…..

How much will a solar panel top up in winter, I mean what sort of amp output would you get on a grey winter day?

Potentially very little, at times negligible.
At the moment my 270W panel is sometimes only reaching 30W output.

You might fare better if you don’t live in Scotland.

If I remember I’ll get a screenshot of the history tomorrow for some numbers.

How much will a solar panel top up in winter, I mean what sort of amp output would you get on a grey winter day?

About 4AH a day is what I was getting out of a 160W panel over Christmas, and the weather was mostly bright – the sun doesn’t clear the rooftops for very long! (60AH+ in mid summer).

It’s enough to keep the batteries topped up, but won’t really cope with much usage.

A bog-standard battery charger used every couple of weeks would be another way of doing it.

Not all split charge systems are the same. Sure, you can pay £20 for one of those matchbox things, or you can get decent kit that you can control from your phone via Bluetooth….
https://voltaconsolar.com/victron-products/victron-dc-dc-converters/victron-orion-dc-dc-converter-chgarger-12-12v-isolated-and-non-isolated.html?utm_medium=cpc&utm_source=google&gclid=EAIaIQobChMIrM7C09-09QIVCuJ3Ch1AxQywEAQYBCABEgJlY_D_BwE

Hmmm I’ll think about solar for the summer, but need sethimg better for winter.

Back to the original question, can I use any size charger, it just takes longer with a lower output one, there’s no real max battery size for a charger?

And does it matter if I’ve 2 batteries in parallel, do I just connect to the terminals of one of them and it’ll charge both?

@vdubber Split charge systems are equally poor if you want to ensure maximum performance. However, your linked product is the other end of the spectrum, DC to DC chargers are the best with intelligent charging and quickly topping off the last few % of battery capacity.

@ed34 I’ve used an under-rated charger as you suggest. It’s fine until you need it most…if the batteries are low, it will trip out the charger as batteries will place a large demand on the charger. (The charger can only control amps, the load determines how many amps will be pulled). I used to be able to use mine normally on the slow charge setting, and then once the charge had increased I could switch to a fast charger as the load decreases as state of charge improves. I’ve now bought an intelligent Ring Smart Charger from Halfords, I don’t know what the ahr limit is but it will rescue a battery that has accidentally discharged to a couple of volts on the ‘I’m an idiot’ setting.

But, I’ve got 400w of solar on the roof and in the winter it easily copes with maintaining my 225ahr battery bank. In the summer the the panels generate enough that I can leave the fridge running all summer without any driving or hookup. Unless you are staying in the van regularly without driving, solar is a proper fit and forget solution that just works away on the background. In the van I’ve got a Ring RSCDC30 which does both battery to battery charging (instead of split charge) and also has a solar charge controller built in.

In parallel, ideally connect to + of one battery and – of the other so that each battery is using one short section of the battery link cable.

Back to the original question, can I use any size charger, it just takes longer with a lower output one, there’s no real max battery size for a charger?

And does it matter if I’ve 2 batteries in parallel, do I just connect to the terminals of one of them and it’ll charge both

Yes, you can treat them as one battery that’s twice the capacity if they’re connected in parallel.

The ‘capacity’ ratings of chargers are very loose guidelines – if you just want to keep them topped up, a 5A charger would be fine. BUT think about getting a bigger charger that would also be of use to recharge the batteries / charge a car battery if needed (would take forever with a 5A charger).

I never had any issues charging my 110ah leisure battery off the van alternator through a voltage sensing relay, though I was using the van as my main transport.

I’d get 3 days parked up (coolbox, led lights, water pump) before it would need topped up.

Have added a solar panel now which works well, especially as I’m not driving the van as much

If you have 2 or more batteries i was always told to take the + from one side and – from the other but that aside the charger will be fine. I have a tiny norco trickle charger for the van battery which works well. The house battery has a charger for the 240v hook up so I can just hook up to a plug in the garage and charge that if I see they are getting low.

Solar is nice but I keep the van in a garage and on a trip the roof is covered in canoes so not a good option for me. Looking at solar blankets currently to see if they might be an option but storage space is then an issue.

I never had any issues charging my 110ah leisure battery off the van alternator through a voltage sensing relay

It works fine, my first van was set up this way. But the charge rate tails off and gets slow. You’d have to do many hours of driving to get the battery topped off the last few percent, may not sound much but you should only discharge lead acid to 50%. So the OP has 2x 115Ah = 230Ah. 50% is 115Ah useable capacity, if you are driving around and not doing long trips and only getting them 80% full, that’s less than 95Ah left.

Compare that to a b2b charger that will place a demand on the alternator until the batteries are full, mine puts in 20-30Ah so that will top them off to 100% in a short trip.

Just because I said I would, here’s some screenshots of my 270W Solar at the moment. Over the last month or so it’s only really got over 10% on one day, the Pmax value, take in to account short days and it’s not giving much.

Compared to the summer where it often gets very close to its 270W (occasionally over 270) and the days are longer.

Hey, @phil5556 – did you try downloading history from the Victron app? I tried to, but it kept hanging every time I pressed the button…

Here’s mine from 160W panels with some shading for part of the day. I was running LED Christmas lights permanently from the start of the graph until ~4th Jan, and the solar wasn’t quite keeping up with them, so the controller was in bulk mode for pretty much all that time (i.e. the battery was taking everything the solar could generate.)

50 Wh is near enough 4Ah

@tillydog I didn’t realise that was a thing but I’m in the van fiddling so just given it a try. On iPhone both share & save to files or open in excel are working fine.

On iPhone both share & save to files or open in excel are working fine.

Ahh – OK, I think it must be something wrong with mine, it worked OK before…

Here’s my summer yield for comparison (the controller was getting to float charge most days, so the yield could have been higher if usage had required it).

(As someone said above, I run the fridge 24/7 in the summer off solar alone.)

Maybe the next update of app or firmware will fix it?

Yeah in the summer my battery is fully charged again by breakfast, the longer days not only help with extra charge we also use much less power as there’s no heating or lights on in the evenings.