Trickle Charger

[GRWXJR]

You've lost me here. How are internal chargers not the correct voltage?

Pat

I'm not an expert, but generally I think its like this..... although all nominally '12v' the actual voltage a charger will put in will vary according to its regulation and indeed how much its able to actually put in in terms of current.

Lots of small 'trickle chargers' might run at say 13.1v. Whereas the charging alternator off the engine will punt in at about 14.4v.

The 'intelligent' stuff monitors the battery condition and ramps down the input current so that the charge voltage remains constant. You don't want the voltage on 'maintenance' to be too high or you'll overcharge and cook an already charged battery (but if the battery is discharged you DO need a decent input voltage and current to charge it effectively and in a reasonable timescale).

The really clever bigger intelligent chargers start with a high volts/high current input, then ramp down the charge voltage as well as the current until you end up with a fully charged battery that is being maintained at a suitable voltage and trickle current.

 

[GRWXJR]

Hi, have had some really helpful replies, thanks, just to answer a question regarding our solar panels not charging the leisure battery, I do live in the UK and have two 60w panels, is this not sufficient enough to keep the leisure battery topped up when not in use?:rolleyes2: Tanya.

Theoretically thats enough to support/charge (say) a 100AH battery.... except for the fact that in the UK esp at this time of year you might only be getting 10% of the potential output of your panels (during daylight hours).

So I'm guessing (cos I don't have any PV panels!) that while it'll help to keep them stable, you might well need to boost the batteries periodically with a more beefy charge source to keep them tip-top.

However, thats not really an informed opinion - more a case of looking at the numbers & drawing an unsubstantiated conclusion - so if you get a more experienced answer - go with that instead of mine :lol-053:!

 

[iampatman]

I'm not an expert, but generally I think its like this..... although all nominally '12v' the actual voltage a charger will put in will vary according to its regulation and indeed how much its able to actually put in in terms of current.

Lots of small 'trickle chargers' might run at say 13.1v. Whereas the charging alternator off the engine will punt in at about 14.4v.

The 'intelligent' stuff monitors the battery condition and ramps down the input current so that the charge voltage remains constant. You don't want the voltage on 'maintenance' to be too high or you'll overcharge and cook an already charged battery (but if the battery is discharged you DO need a decent input voltage and current to charge it effectively and in a reasonable timescale).

The really clever bigger intelligent chargers start with a high volts/high current input, then ramp down the charge voltage as well as the current until you end up with a fully charged battery that is being maintained at a suitable voltage and trickle current.

Ok, thanks for that. I understand what you are saying but still don't understand why the charging units fitted to motorhomes, Calira, Schaudt etc, are not suitable for charging the leisure battery providing your battery or battery bank is not greater than the output of the unit. If they are not appropriate why are they installed?

Pat

 

[Obanboy666]

I also find it bizarre that the charger in my 2013 Swift motorhome is apparently not adequate / appropriate for my batteries.
Coincidentally I checked my battery display on the main control panel at lunchtime and decided to put the mains on to charge the batteries up before I go away Saturday and it showed the leisure batteries @ 12.5 volts.
Looked 1/2 hr ago and the control panel showed the leisure batteries @ 14.1 volts.
can anyone give me a clue as to what that means ? Is the charger putting 14.0 volts + into the batteries ?

 

[Debs]

Ok, thanks for that. I understand what you are saying but still don't understand why the charging units fitted to motorhomes, Calira, Schaudt etc, are not suitable for charging the leisure battery providing your battery or battery bank is not greater than the output of the unit. If they are not appropriate why are they installed?

Pat

Unfortunately motorhome manufacturers are still under the impression, that when you go somewhere you will go to a campsite and be hooked up to mains electric, and there is a whole industry out there waiting for you to spend your cash getting upgrades. Not surprising then that many motorhomes are delivered with one 85ah battery, which is woefully inadequate for today's needs.:rulez:

 

[iampatman]

Unfortunately motorhome manufacturers are still under the impression, that when you go somewhere you will go to a campsite and be hooked up to mains electric, and there is a whole industry out there waiting for you to spend your cash getting upgrades. Not surprising then that many motorhomes are delivered with one 85ah battery, which is woefully inadequate for today's needs.:rulez:

Yep, I'd agree with you there that an 85ah leisure battery is, or may be, inadequate. It depends what you are powering in your MH and how you adapt it. If folk want to run TVs, coffee makers, kettles, vacuum cleaners, clothes irons, laptops, invertors, microwaves etc..etc.. then theyre going to run out of battery juice pretty quick if they're not on EHU. I think there are three ways to approach this.
1) Carry out an audit of how much juice you need and how you can adapt your MH (eg.change to LED lights, fit solar panel/s, buy generator, lose the vacuum cleaner and buy a brush, is an invertor really necessary)
2) Check the charging capacity of your charging unit. I've said this on earlier posts but I made the mistake of fitting 2 X 110ah leisure batteries and then discovered that my charging unit is rated at 20a which means it will charge 200ah of batteries. In my case I've got 220ah LBs and that added to, say 50%, of my engine battery means the unit fell over when asked to charge approximately 260ah of batteries. No surprise there!
3) I think solar panels are the way forward but I would urge folk to have a look at these articles/websites before fitting the biggest panel they can and then stuffing their MHs with as many batteries as they can. It's not that simple.

UK Caravans, Caravan Information, Caravan Reviews, Caravan Forum, Sales, Campsites ->Caravan Forums Ignore the adverts on here, the articles are really useful.

A and N Caravan Services : Battery Charging Faults - Schaudt Elektroblock, Reich E-Box, Calira, CBE, Arsilicii and Nordelettronica Battery Chargers supplied and Repaired I've got no connection with these people but their information on batteries/charger failure and solar panels seems to make sense to me.

I've found my 100w solar panel and the charge from the alternator when driving almost daily has kept my 2X110ah batteries topped up nicely whilst in Europe this spring and summer just gone. We don't use much juice. The problems I've got now have arisen since we've been on EHU.

Mind, I'll stand to be corrected on my observations.

Pat

 

[GRWXJR]

I also find it bizarre that the charger in my 2013 Swift motorhome is apparently not adequate / appropriate for my batteries.
Coincidentally I checked my battery display on the main control panel at lunchtime and decided to put the mains on to charge the batteries up before I go away Saturday and it showed the leisure batteries @ 12.5 volts.
Looked 1/2 hr ago and the control panel showed the leisure batteries @ 14.1 volts.
can anyone give me a clue as to what that means ? Is the charger putting 14.0 volts + into the batteries ?

It must be. I'd keep an eye on the voltage in case there's an issue though. Hopefully your charger is doing a full cycle charge, and youll see the voltage fall to more like 13 ish volts with the charger still on. That'd suggest the charger has reduced its rates to a maintenance level, and is working well.
If it holds the batteries at 14+v indefinitely, then that suggests that the charger is defective and just shunting in at full whack constantly, which will cook the cells.

If you isolate a fully charged healthy battery, let it stand a while then measure its voltage itll be around 12.5 ish volts.

A battery needs to be kept within a pretty tight window of voltage, with each nominal 2v cell working between a peak of 2.3v (14v) at the fully charged end, and just over 1.95v per cell (11.7v). Below this the output performance versus volts drop plummets and youll kill the battery in short order.

Battery output is based on fully charged to wiped out, so in reality if you want to get decent life you only get to use about 50% of the rating. Also batts are much better at doing small percentage loads for extended periods than they are at large percentage loads for even brief periods. Having more storage is fine as long as you have enough charge power for a long enough uninterrupted duratio to charge them properly, but youd have to say that reducing consumption to a minimum is the best answer!

 

[Obanboy666]

It must be. I'd keep an eye on the voltage in case there's an issue though. Hopefully your charger is doing a full cycle charge, and youll see the voltage fall to more like 13 ish volts with the charger still on. That'd suggest the charger has reduced its rates to a maintenance level, and is working well.
If it holds the batteries at 14+v indefinitely, then that suggests that the charger is defective and just shunting in at full whack constantly, which will cook the cells.

If you isolate a fully charged healthy battery, let it stand a while then measure its voltage itll be around 12.5 ish volts.

A battery needs to be kept within a pretty tight window of voltage, with each nominal 2v cell working between a peak of 2.3v (14v) at the fully charged end, and just over 1.95v per cell (11.7v). Below this the output performance versus volts drop plummets and youll kill the battery in short order.

Battery output is based on fully charged to wiped out, so in reality if you want to get decent life you only get to use about 50% of the rating. Also batts are much better at doing small percentage loads for extended periods than they are at large percentage loads for even brief periods. Having more storage is fine as long as you have enough charge power for a long enough uninterrupted duratio to charge them properly, but youd have to say that reducing consumption to a minimum is the best answer!

Many thanks for your explanation. I have it on mains overnight so I will check in the morning and hopefully it will have reduced to the maintenance level. Fingers crossed it will have.

 

[GRWXJR]

My (limited) knowledge of battery charging is mainly to do with much (MUCH) bigger battery packs (think industrial Fork Lift or Milk Float sort of sizes) being employed on off-grid properties.

The chargers for those though are basically just bigger versions of what you'll use in your MH, so the philosophy and method should be pretty much the same I reckon.

Its worth knowing that battery voltage measurement alone doesn't guarantee that a battery is fully charged - if you put enough current fast into a battery, its voltage will come up v quickly. However it needs TIME to charge properly. This is why just putting a huge charger onto a battery isn't the answer - you need to charge at an appropriate level, for an appropriate duration. A "Bulk" (see below) charge rate (so charger rating) of 10% & not more than 15% of your battery capacity in AH is a good rule of thumb for charger size.

To try to do this for you without the need for you to faff about, an intelligent charger would put a battery through 3 stages to charge the battery:

Stage 1. BULK. This is where the charger pumps in its maximum current - until the battery reaches the peak charge voltage (which is programmed into the charger, and maybe as much as 14 - 14.4v)

Stage 2. ABSORBTION. The charger reduces the charge current so that the battery is maintained at the peak voltage for a pre-set time (possibly 3 or 4 hours). This is to boost the Specific Gravity of the cell electrolyte and charge the plates fully without over-charging & damaging the battery.

Stage 3. FLOAT. The charger backs off the current further to a bare 'trickle', allowing the voltage in the battery to drop back to a level just above its fully charged and rested level (perhaps 13v ish). It'll then maintain the battery like this for as long as the charger remains connected (& the battery isn't being discharged by loads).

If your charger isn't powerful enough, then it might never get your battery to the peak voltage in Stage 1 (or perhaps take a very, VERY long time to do so).
A smaller intelligent charger like an Optimate can be great at KEEPING a well-charged battery sustained, as it only really needs to do Stage 3 for you - but you need something with a bit more heft if its going to properly cycle your battery setup.

(Disclaimer :dance: I know a little, & I know this can be a dangerous thing! I make no claims to be any kind of expert nor authority on the black art of batteries - I'm just sharing what I have picked up. So - if someone with better credentials than me says something different, listen to them instead!)

To add... perhaps we ought to bear in mind that your Van does have a powerful enough charge source on-board - the charge alternator. So this will charge the batteries well in transit. So (in defence of the builders) perhaps it is reasonable that they might expect a van to have a pretty well charged battery on arrival at an overnight stop, & that the 'mains' charger on board doesn't need to be bigger and more powerful than they often are? I expect its only those who stay off EHU, and then also stay in one place for an extended period (so the engine charge alternator doesn't boost the battery) that ever really struggle with not enough storage/not enough charging?

 

[Obanboy666]

My (limited) knowledge of battery charging is mainly to do with much (MUCH) bigger battery packs (think industrial Fork Lift or Milk Float sort of sizes) being employed on off-grid properties.

The chargers for those though are basically just bigger versions of what you'll use in your MH, so the philosophy and method should be pretty much the same I reckon.

Its worth knowing that battery voltage measurement alone doesn't guarantee that a battery is fully charged - if you put enough current fast into a battery, its voltage will come up v quickly. However it needs TIME to charge properly. This is why just putting a huge charger onto a battery isn't the answer - you need to charge at an appropriate level, for an appropriate duration. A "Bulk" (see below) charge rate (so charger rating) of 10% & not more than 15% of your battery capacity in AH is a good rule of thumb for charger size.

To try to do this for you without the need for you to faff about, an intelligent charger would put a battery through 3 stages to charge the battery:

Stage 1. BULK. This is where the charger pumps in its maximum current - until the battery reaches the peak charge voltage (which is programmed into the charger, and maybe as much as 14 - 14.4v)

Stage 2. ABSORBTION. The charger reduces the charge current so that the battery is maintained at the peak voltage for a pre-set time (possibly 3 or 4 hours). This is to boost the Specific Gravity of the cell electrolyte and charge the plates fully without over-charging & damaging the battery.

Stage 3. FLOAT. The charger backs off the current further to a bare 'trickle', allowing the voltage in the battery to drop back to a level just above its fully charged and rested level (perhaps 13v ish). It'll then maintain the battery like this for as long as the charger remains connected (& the battery isn't being discharged by loads).

If your charger isn't powerful enough, then it might never get your battery to the peak voltage in Stage 1 (or perhaps take a very, VERY long time to do so).
A smaller intelligent charger like an Optimate can be great at KEEPING a well-charged battery sustained, as it only really needs to do Stage 3 for you - but you need something with a bit more heft if its going to properly cycle your battery setup.

(Disclaimer :dance: I know a little, & I know this can be a dangerous thing! I make no claims to be any kind of expert nor authority on the black art of batteries - I'm just sharing what I have picked up. So - if someone with better credentials than me says something different, listen to them instead!)

To add... perhaps we ought to bear in mind that your Van does have a powerful enough charge source on-board - the charge alternator. So this will charge the batteries well in transit. So (in defence of the builders) perhaps it is reasonable that they might expect a van to have a pretty well charged battery on arrival at an overnight stop, & that the 'mains' charger on board doesn't need to be bigger and more powerful than they often are? I expect its only those who stay off EHU, and then also stay in one place for an extended period (so the engine charge alternator doesn't boost the battery) that ever really struggle with not enough storage/not enough charging?

I have just checked the Battery status display on the Sargent unit and it's shows 13.4 volts on the leisure and vehicle batteries and the charger is putting out 1.8 volts. I assume this is the float cycle.
I have 2 x 105 amp leisure batteries and the charger according to the handbook puts out 25 amps, I assume this is max output.
To date I have not had any problems with usage and can comfortably manage 2/3 days without moving. All the lights are led but I do use the tv and sky box through a small inverter.
I have a folding solar panel that I use when the sun shines which obviously helps.
Ideally I would like to leave the ehu on 24/7 on my drive but the local scumbags have already tried to pinch the cable so I normally disconnect it on a night.

 

[GRWXJR]

From what you've posted there - I'd say that your onboard charger is doing the job very nicely Obanboy666!

You have 2 x 105AH 12v battery's - so that's 210AH @ nominal 12v.

So your charger works out to have a theoretical potential input on 'BULK' charging of 12% of the total storage rating - ideal! No wonder your battery pack charges well IMO - you have a well-balanced charge/storage setup, and an intelligent charger regime.

Mathematically I reckon you have 2.52kW of storage, which is probably 1.26kW useable at 50% discharge limit.

 

[Wooie1958]

Float / Maintenance charges from onboard Mains Chargers are normally either 13.5 volts or 13.8 volts.

It sounds like it`s working fine.

 

[Obanboy666]

Many thanks to all for the sound advise, best thing I did joining this forum.
I was just recalling when I got my caravan 3 years ago, clueless regarding batteries etc, etc. It was kept in storage and we would often find the motor mover wouldn't move the caravan when we went to hitch up. The battery was obviously as flat as a pancake.
As I recall when I bought the caravan new the dealer didn't mention anything about the battery and how to look after it. And neither did the motorhome dealer when I picked that up come to think about it !
I reckon it should be part of the handover especially for someone like myself who was new to caravans and motorhomes bearing in mind how much batteries cost.