Charging system for a minimal camper?

[HarryInHudds]

Hi folks, I'm making inroads through the mechanical work of building out our "new" Ducato (2016 Eu5+, thus dumb alternator, tbc), and am now trying to get a shopping list for the electrics. {sorry if this is repetitive, but searching hasn't revealed a answer for a non-max'ed out solution, i.e. at limited cost}

Our principal use of 12v is an Alpicool chest fridge, plus some for new toys: a Maxxfan roof fan and a Chinese heater; though I doubt we'll use them on the same day!
We have minimal LED lights, no TV, no inverter etc.
Over 9 seasons in the old T5 the leisure battery (basic 85Ahr) only starting dropping off after 2 full days parked (or 1 and a bit if in Spain). We tour, and drive most days for 1-2 hours.

So my question is:
if I want a slight upgrade, to guarantee 2 days without driving, and possibly 3, should I fit
a) more battery (eg 2 x 110 AGM) or
b) a fancier charger - Victron B2B - to charge the battery fuller and quicker than a VSR etc.
c) both?
I'm not going solar yet; though am open minded, - treating it as a non-essential upgrade for another year.

also: does going AGM require a better charger than plain VSR?

Thanks, Harry

 

[trevskoda]

I would have fitted led carbon batts, pos 2 for sure, but remember it takes twice as long to charge them, but the l carbon does not suffer sitting at a lower charge than standard or agm batts, solar is for sure a good upgrade but only good from spring to aut.

 

[Squiffy]

Hi folks, I'm making inroads through the mechanical work of building out our "new" Ducato (2016 Eu5+, thus dumb alternator, tbc), and am now trying to get a shopping list for the electrics. {sorry if this is repetitive, but searching hasn't revealed a answer for a non-max'ed out solution, i.e. at limited cost}

Our principal use of 12v is an Alpicool chest fridge, plus some for new toys: a Maxxfan roof fan and a Chinese heater; though I doubt we'll use them on the same day!
We have minimal LED lights, no TV, no inverter etc.
Over 9 seasons in the old T5 the leisure battery (basic 85Ahr) only starting dropping off after 2 full days parked (or 1 and a bit if in Spain). We tour, and drive most days for 1-2 hours.

So my question is:
if I want a slight upgrade, to guarantee 2 days without driving, and possibly 3, should I fit
a) more battery (eg 2 x 110 AGM) or
b) a fancier charger - Victron B2B - to charge the battery fuller and quicker than a VSR etc.
c) both?
I'm not going solar yet; though am open minded, - treating it as a non-essential upgrade for another year.

also: does going AGM require a better charger than plain VSR?

Thanks, Harry

In my experience the best solution for battery longevity of charge is without doubt solar panels, if you drive for 2-3 hrs per day when touring then improving your mechanical charging is good but as soon as you stay for 2-3 days in one place there is nothing to beat solar panel(s) with a good Regulator MPPT style, so my advise for the cost if you are able to fit them yourself is only one solution (Solar) . Phil

P.s. Or a 1kw petrol inverter generator is a good back up.

 

[HarryInHudds]

Thanks;
@Trev, I'd not clocked that Lead Carbon as an option. the deep cycle ability is good, but how much longer do you need to charge them? Is there a charge rate rule of thumb (like the C/5 for lead acid)?
Superficially it seems they may have 50% more useable power, but cost 50% more--- so is the benefit a longer life?
It sounds like an option for when you've got solar... so charging time is less of an issue.

@Squiffy, I understand that with solar, I just expect I'll be "vanned out" by the time its hits a minimal spec, which probably doesn't include stuff on the roof. I'm doing quite enough wacky development work with it, so I'm anticipating being fed up, and needing to use the thing to regain some sanity... Not to mention my immeasurably patient partner!
And for me, no way do I want a gennie, unless we start going to total wildernesses etc. -Sorry

 

[Squiffy]

No probs Harry, I know how you feel and what it takes to get through a build. .Phil

 

[wildebus]

Hi folks, I'm making inroads through the mechanical work of building out our "new" Ducato (2016 Eu5+, thus dumb alternator, tbc), and am now trying to get a shopping list for the electrics. {sorry if this is repetitive, but searching hasn't revealed a answer for a non-max'ed out solution, i.e. at limited cost}

Our principal use of 12v is an Alpicool chest fridge, plus some for new toys: a Maxxfan roof fan and a Chinese heater; though I doubt we'll use them on the same day!
We have minimal LED lights, no TV, no inverter etc.
Over 9 seasons in the old T5 the leisure battery (basic 85Ahr) only starting dropping off after 2 full days parked (or 1 and a bit if in Spain). We tour, and drive most days for 1-2 hours.

So my question is:
if I want a slight upgrade, to guarantee 2 days without driving, and possibly 3, should I fit
a) more battery (eg 2 x 110 AGM) or
b) a fancier charger - Victron B2B - to charge the battery fuller and quicker than a VSR etc.
c) both?
I'm not going solar yet; though am open minded, - treating it as a non-essential upgrade for another year.

also: does going AGM require a better charger than plain VSR?

Thanks, Harry

It really is just a matter of doing the maths....
The main use of power is going to be the fridge. You would be extremely hard pushed to get 2 full days out of a 85Ah battery safely, running the fridge and anything else. What is the average Ah/HR quoted for the fridge? That should be in the user manual or spec sheet.

Chinese heater. Call it 1Ah/HR. How many hours do you expect - or want to be able to run it?
Maxxair fan. You can call that 1 Ah/HR as well. Same question as Chinese heater.
As you say, unlikely to be using both at same time, but certainly possible to want to use the fan during day and heater in evening (I have).


Old battery started "dropping off 2 days".... What does "dropping off" mean? 12V stuff stop working as voltage too low to power it? Or hitting a certain voltage you preferred not to go below?
What 12V stuff have you got in the old T5 that you will use in the new van? Less, more?

Charging... You don't intend to have solar. You want to be off grid. If you then have a VSR for driving, the reality is you don't have ANY way to properly charge your batteries. The alternator is not a battery charger. It is a power supply and will not charge any batteries optimally, so your "100Ah" battery for arguments sake will end up being maybe a 85Ah max. If you follow the rule of not discharging below 50% of quoted capacity, you will have a whopping 35Ah (85 - 50) to last you a full weekend.
You need at least one actual battery charger to get a full - and decent level of - service from a battery. A VSR is ok if you had say a good solar controller to finish the job, or hooked up reasonably often to do so, but otherwise not the best option.

 

[Derekoak]

It's all very complicated. It sounds like my electric needs are very similar to yours, (except the max fan which surely goes really well with solar) I have a smaller, fiat doblo xl 2017. I wanted lithium but in 2018 lithium was too much so I got an interim 85 ah agm 30 amp b2b and mppt, ring dscdc30, and 160 w solar. We drive every day but perhaps only 20 minutes.
After 4 years the agm was deteriorating and the ring which is a good cheap double use idea was not performing. The solar which is great except winter, even in Spain, could be a luxury. I now have 200ah self assembled lithium cells, a victron lict split charge relay (VSR to you) the same 160 w solar and a victron mppt.
What follows is different to others views but I think they are after the best rather than cheap and good enough. If I was after minimal after my experience I might think of a a small lithium battery. My 200ah will last at least 4 days standing still with solar off so I suggest 100ah lithium should be fine. But as Wildebus says do the maths lithium can be almost completely discharged say 95 to 85% DOD, or maybe 200 ah lead carbon. I know little about lead carbon. Both of these chemistries do not mind sitting at partial state of charge, whilst Agm and flooded lead do. I would not get those batteries. Then if you want to avoid solar and want to charge those batteries cheaply put in a victron vsr suitable to the chemistry or follow trevskoda and have a manual switch activating a power relay to connect your leisure battery with your alternator a few minutes after starting driving and remembering to switch off when you switch off the ignition.
My victron lict connected by 3m of 16mm copper gives 65 to 40 amps to my battery all the way until the 200ah lithium fe po4 battery is full. The voltage only varies from say 12 volt of a low lithium Soc to 14 v where I set my Bms to stop charging.
My fiat 120a alternator shows no sign of strain. I do not know so much about lead carbon but if it can sit at partial charge without damage what is the point of fussing with an expensive b2b? Agm and flooded lead really need a b2b to charge them fully but lithium does not, at least with my fiat alternator.
The lict only cost about £80. A spare 250a power relay I could sell you for £30 plus postage. If you can wait 6 weeks as I am in Spain .
I would have solar when I could but you could do without if you drove to recharge.
Lithium does need to be above 5C when charging but is otherwise wonderful.

 

[HarryInHudds]

Thanks for the replies:

In the past I've found that the T5's fridge (Vitrifrigo 39l front loader) might struggle to start up after the second morning. Voltage probably 12V resting, showing 8ish during a failed start up. Some of this may be cable thickness, but I inherited this. I would switch off at this point, on run it from the starter battery for a bit. I know this isn't great, and the battery may be past it's best, (though it hasn't been abused beyond 5or6 mornings as described), however this simplistic £150 setup does the job 90% of the time.
I've not checked the new fridge's average consumption rating, peak I think is 5-6A, but being a top loader I anticipate a reduced "on" time.

I'm already with much of your suggestions, my current thinking is 2x115/105 AGMs, with a 30A B2B charger, more for speed and completion of charging than because my alternator needs it (I don't think it does). I don't see we'll get the benefit for the extra cost of Lead carbon or Lithium for our sort of usage, I'm already nudging £500.
We've just had 17+ years out of the OE lead-acid starter battery on my wife's Citroen... they can last, at least when kept topped up.

Specs for AGMs seem confusing, some claim 60%DOD, some 80%DOD - possibly determined on whether they are also happy for cranking. Is this real? (I've generally been looking at Alpha, being close enough to take it back if needed).
I'm a bit wary of DIY lithium installs, after colleague had his brand new VW Shuttle written off from a fire under the front seat, believed to have been started by a surge from a lightening flash on his solar... Not totally sure as he was a bit cagey about it! with no pay out as it wasn't insured as modified at that point.

As a side point: do Victron 30A B2B's give any real benefit over say a Votronic one, other than being blue and having bluetooth? How is the £50+ premium justified?
Thanks, Harry

 

[wildebus]

Just point on wiring fridges... It is remarkable how many installations of compressor fridges use underspec cable. Including ones from professional conversion companies.
I think the installers read the specs, see either a "1.2A average draw" or "5A when running" or whatever and look up what cable is needed for 1.2A or 5A. And then the owners wonder why when their battery is still at a decent level the fridge won't start due to low voltage.
A compressor fridge can take upto 10x or more the running Amps to start the compressor. This high current will cause a voltage drop and stop the fridge starting and the only way round that is to use the right cable to reduce the drop. Depending on length of run, 4mm2 is minimum, 6mm often needed and sometimes 10mm could be required.
(PS. Same rules apply with deisel heaters to a lesser extent).

If you battery is dropping to 8V AT THE BATTERY when the fridge trys to kick in and was at 12V just before, it sounds knackered. That would be a battery issue not wiring.
The needs of a starter battery is quite a bit different to a leisure battery so can't really compare use and life between them.

 

[Derekoak]

I would be wary of diy lithium it is time consuming and you do not want to go there.
However I still think you should avoid agm and flooded lead. Both sulphate if left partially charged. Your starter battery that lasted years was always charged again immediately after discharge. Your leisure battery does not get that treatment?
My experience with agm is that more than 50% and they deteriorate rapidly. They do need a b2b to charge them to 100% again and you need to drive enough each day to do it. It you double the battery you need to double the recharge after using them fully. That is even longer at partial discharge. Rather than 2 agm and a b2b, apparently less Lead carbon and a vsr sounds worth it if you cannot face the one off cost of lithium.

 

[Nabsim]

Re the B2B, I have been using a Votronic 30amp for a couple of years or more. I don’t think Victron did them at that time but I wouldn’t pay the extra that they cost. I do have a Victron battery monitor (needed when I changed to Lifepo4) so I can see what amps are going in very easily but suffice to say it does what it’s supposed to.
I have some Victron bits but my opinion only I don’t think they are any better than Votronic, the only gain is Bluetooth, against the the Votronic kit is much smaller and easier to fit in. Votronic kit was always designed for mobile or boat use where I think Victron came from solar farm type side hence much chunkier. I run a Votronic mppt side by side with a Victron mppt and if anything I get very slightly more performance with the Votronic but not enough to matter. Tenths of an amp at this time of year and seems to level out in summer.
So, you want to see what happening on your phone and have the space go with Victron, if you just want it to work without being able to check on your phone go Votronic. As I said, my opinion only as someone who uses both brands

 

[Nabsim]

If I were you I would seriously consider a 100W folding panel or a lose 100W panel you can lean against the van. When you are parked up it has to be solar or a genny or both

 

[HarryInHudds]

Various points here:
Yes, I'll get solar if/when we stay in the same place long enough not to charge by driving. Mobile ones are a good idea too that I've seen in use but had forgotten, thanks for the nudge.
Its hard to work out what the Victron bluetooth ap actually does. Is there a proper Amps readout? (or graphing)? If it's simply for a one-off programming, then voltage, I can fit a sub £10 voltmeter that would be much easier to read.

Our usage as a holiday wagon optimistically is about 40 nights a year. Half of those will use neglegable power, maybe 4-6 wilI stretch the battery. So the difference between 100 recharges and 1000 seems irrelevant, if I can avoid killing it by over discharge.
Picking up on Dave's previous calc, our new fridge's spec says 0.2kw/hr per 24 hrs, which I equate to 17Ah. (this matches with killing the useful capacity of our old battery in 30-35 hrs).
However the calc for a proposed system would be
220Ah of AGM x 60% DOD x 100% charge via B2B = 132 usable Ahr, (a massive step up from the 39 mentioned on the old van).
Our usage of 17Ahr, with say 6Ahr added for a fan or heater (so 23Ahr use/day), would give me 5.5 days.

However Derek's suggestion with a single PbC AGM gives
110Ah x 80% DOD (occasionally) x 100% charge = 88 usable Ahr, @ 23Ahr/day =3.8days, so still achieves our target.
eg https://www.alpha-batteries.co.uk/1...ad-carbon-ultra-deep-cycle-battery-dc12-100c/.
The reduced capacity would be offset not killing it at higher DOD, and by quicker charging. (I assume suggesting a VSR was a mistake?)
When we need more, I'll add solar.
This solution is also £50 cheaper, which is nice, as we're not using it enough to justify a max'ed out solution. Otherwise I'd have a new 4x4 Sprinter... ;-)

So I have a conclusion! thanks for the help to all .
(though I'd still like to know if the Victron app shows current...)

 

[Derekoak]

No it may be controversial but I was suggesting that as lead carbon is happy at partial charge you could save money with a cheap vsr rather than a more expensive b2b. Your lead carbon would charge quickly at first with the vsr if the cables were big enough, say at least 16mm, but might slow down more than a b2b before 100%, but does that matter as much as the initial faster charge and money saving?

 

[Derekoak]

I used to have a 140 pound 30 amp b2b and agm battery and got 30 amp falling quickly to 20 and down to 5 amp whilst driving. Now I have a cheap vsr and bigger cables and get up to 65 amp charge rate falling to 40 then my lithium is full. If lead carbon charges more easily than flooded lead and Agm, you may get a similar result with that although I have never had lead carbon.

 

[HarryInHudds]

As far as I can see, every outlet selling Lead Carbon AGM (or plain AGM) prefixes their offer "if you've got a suitable charger".
Does this mean "do not use with a smart alternator, as it peaks at >15V"? -thus a trad alternator at 14.4V etc is safe?
Or: you don't get the phased charge profile that makes the thing last?
And presumably you don't get the float charge, so only reach c85% of nominal capacity.

It's interesting that you're using a Lithium on a plain VSR supply - I thought that was totally forbidden! - However not a direction I'm considering yet.

 

[wildebus]

As far as I can see, every outlet selling Lead Carbon AGM (or plain AGM) prefixes their offer "if you've got a suitable charger".
Does this mean "do not use with a smart alternator, as it peaks at >15V"? -thus a trad alternator at 14.4V etc is safe?
Or: you don't get the phased charge profile that makes the thing last?
And presumably you don't get the float charge, so only reach c85% of nominal capacity.

It's interesting that you're using a Lithium on a plain VSR supply - I thought that was totally forbidden! - However not a direction I'm considering yet.

".... a suitable charger ...." is meaning that to properly charge some batteries you need to fed them with sufficiently high voltage. Most alternators don't go high enough, and all a VSR is is an automated switch which will not make it better.
End result is you never properly charge the battery and they will not give you the full quoted capacity. A Lead Carbon battery is better at dealing with PSOC but it still will not give you the full capacity as it may never recharge fully.
It is not a no-no to have a VSR with an AGM, as long as you have another method to charge the battery properly on a regular basis, but if driving IS your battery charging solution, you need a proper charger, not a relay.
That 100Ah battery you are looking at might give you 35Ah of usable power after a 10 hour drive to "recharge" it.

Relay with Lithium. Many people do it. You can if you have a relay that will cut off at the appropriate time to avoid over-voltage protection kicking in.
Personally speaking I would not use alternator charging via relay with Lithium as I prefer to have more control over the current draw and output.
It is easy to overload an alternator, especially on older vehicles and a visit to a garage to get an alternator replaced is more expensive than a B2B. (I am NOT referencing the infamous Victron video on the alternator blowing up here, in case anyone thinks that).

Ref the Victron .... I think it shows the voltage IN and voltage OUT, no current. Is it better than the Votronic? Probably. Worth the extra money? For you to decide. There are a lot of B2Bs out there which don't run at their stated capacities for very long as they overheat. I know the Victron units and the Ablemail ones will work at full capacity for hour after hour. I have never tested the Votronic one so don't know what camp that falls into.

 

[Derekoak]

OK if lead acid needs a high voltage to charge, higher than for example the 14.25v of my alternator then lead carbon does not work. All I know for sure is that my lithium is fully charged below 14.2v so my alternator and a vsr does a very fast job. My battery management system that is a prerequisit of lithium stops charge when I wish. So it sounds as if the only chemistry that works with a vsr is lithium. Sorry to suggest that it may be otherwise Harry.

 

[Derekoak]

It's interesting that you're using a Lithium on a plain VSR supply - I thought that was totally forbidden! - However not a direction I'm considering yeyet.

I just copied what Phil, (the Boss) was doing.

 

[wildebus]

OK if lead acid needs a high voltage to charge, higher than for example the 14.25v of my alternator then lead carbon does not work. All I know for sure is that my lithium is fully charged below 14.2v so my alternator and a vsr does a very fast job. My battery management system that is a prerequisit of lithium stops charge when I wish. So it sounds as if the only chemistry that works with a vsr is lithium. Sorry to suggest that it may be otherwise Harry.

A VSR can be used with Lead - and is very common. But to treat the batteries right, you need the use of a Smart Charger to finish off the job at least on a regular basis. Could be a mains charger; could be a Solar charger, but one or other if no B2B fitted.