Can i charge my 2nd Battery with my Inverter

Submitted: Monday, Jan 01, 2024 at 20:33
ThreadID: 146771 Views:1560 Replies:7 FollowUps:10
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Hey guys,
We bought our campervan, a converted Peugot expert 2009, a week ago. Unfortunately, the seller no longer answers our questions, for whatever reason. That's why we're trying here, thanks in advance!
We have a second battery, which is charged once via the engine and once via solar power. We also have an AC/DC inverter and wanted to ask whether we could also charge the second battery with external power via this or whether we need an extra setup for this. If this is not possible, what kind of setup do we need?
Kind regards
Leon
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Reply By: RMD - Monday, Jan 01, 2024 at 21:48

Monday, Jan 01, 2024 at 21:48
Leon
What you have there is not an AC to DC inverter but a DC to AC, ie, DC12v to SINE WAVE AC power, ie 240v AC. Well, that is what it looks like to me! IF so, No, you cannot charge the battery with it!
It USES DC input to it from the battery to change it (INVERT IT), to 240VAC for use with relatively small 240V AC appliances.

To charge the battery, in addition to the solar and engine systems you mention, you would require a 240Vac input Battery charger, preferrably a multi step charger which will stop charging when the battery is fully charged. example: a 5 ampCTEK multi stage unit would do the job. There are bigger sizes at additional cost.

Using the inverter you have, running off the ORIGINAL battery, it's 240v ac output could be used with the above mentioned 240v ac battery charger to charge an auxiliary battery. Not a recommended method though. Ony for emergencies and well monitored for safety and duration of drain on OE battery.
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Reply By: Member - John - Tuesday, Jan 02, 2024 at 10:44

Tuesday, Jan 02, 2024 at 10:44
Agree with first post, but more pertinent to me is that the battery doesn't look to be secured other than by the cut outs in the wooden beam above? Is it secured any other way?
John and Jan

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Reply By: Tim Owen - Tuesday, Jan 02, 2024 at 14:36

Tuesday, Jan 02, 2024 at 14:36
You need an 240 volt battery charger. You need to ensure the charger is suitable to the 'chemistry' of the 12v battery (ie. lead acid vs lithium etc), and then you need to determine how much current it needs to deliver (ie. how big it needs to be). With those 2 parameters you can go shopping and I'm sure there will be plenty of suggestions of specific products here.

Chargers delivering higher current (amps) take less time to charge the battery. In general, chargers with higher current ratings are physically larger and more expensive.

You should be driven by your use case. Essentially, do you want to 'trickle charge' it over a few days or longer (in which case <=5A would probably do), do you need it to charge overnight (in which base maybe 10A would do for a 120AH battery), or do you want to be able to charge it in a few hours - in which case you might want something larger.

You can have the charger permanently connected to the battery there with the inverter, and just plug it in to 240V mains when available.
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Follow Up By: qldcamper - Wednesday, Jan 03, 2024 at 07:26

Wednesday, Jan 03, 2024 at 07:26
With lead acid batteries, which includes AGMs you should have a charger with a current rating at least 10% of the AH capacity of the battery if it is a 3stage or higher so called smart charger, or you run the risk of it never being able to switch into float and causing excessive gassing and electrolyte loss.
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Follow Up By: RMD - Wednesday, Jan 03, 2024 at 09:10

Wednesday, Jan 03, 2024 at 09:10
QLD
Is that really true. If you pump it up with 10amps it will still get to the same state of charge with a 5 amp unit. Mine does it ok all the time and cuts off when charged. 5 stage.
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Follow Up By: qldcamper - Wednesday, Jan 03, 2024 at 13:00

Wednesday, Jan 03, 2024 at 13:00
It will charge it RMD but the current may never drop low enough to kick the charger out of absorption into float.
This was addressed in a tech bulliten put out by I think century batteries (may be wrong on that) when they had a lot of batteries failing after multi stage chargers were released.
Seemed illogical that smaller could over charge but made sense when you read it.
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Follow Up By: Allan B (Sunshine Coast) - Friday, Jan 05, 2024 at 11:19

Friday, Jan 05, 2024 at 11:19
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Yes, it does make some theoretical sense QC. Perhaps if an unhealthy battery has sufficient internal current leakage to maintain the charge current above the threshold of the charger's algorithm.
I have not seen it happen but most of my battery experience was prior to multi-stage chargers. In those early days it was common to 'hook it up and bring it to the boil'!
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Allan

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Follow Up By: qldcamper - Saturday, Jan 06, 2024 at 11:10

Saturday, Jan 06, 2024 at 11:10
The good old days, life was so much simpler back then.
I put much of it down to social media.
People that know nothing convincing people they need something they dont then companies produce a product that they dont really need and sell it to them and they are then happy but have no clue what the thing actually does.
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Follow Up By: Allan B (Sunshine Coast) - Saturday, Jan 06, 2024 at 13:25

Saturday, Jan 06, 2024 at 13:25
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That's what I liked about the deserts and an old Troopy. It was all so simple.
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Allan

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Reply By: Member - Cuppa - Tuesday, Jan 02, 2024 at 14:42

Tuesday, Jan 02, 2024 at 14:42
Back when we first got interested in RV's, before dc to dc charging of aux batteries became common the standard way most folk charged their aux batteries whilst driving was to have an inverter connected to their crank battery (often via a VSR ' Voltage Sensitive Relay to ensure that the crank battery would not be inadvertently flattened after the ignition was turned off) & a 240v mains charger plugged into the inverter, to charge the aux batteries.

The risk with this is there is a live 240v cable between the the inverter & charger whilst driving, & potentially in an accident scenario if this cable were damaged it could make the entire metal body of the vehicle live, possibly 'frying' anyone who came to the rescue.

This potential was reduced greatly by a) making sure the cable between inverter & charger was as short as possible & b) by taking steps to protect it from possible accident damage.

To charge your batteries from external mains power will require a 240v mains battery charger.
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Follow Up By: Allan B (Sunshine Coast) - Tuesday, Jan 02, 2024 at 15:15

Tuesday, Jan 02, 2024 at 15:15
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No Cuppa, it could not make "the entire metal body of the vehicle live".
It could only do that if there were a second connection to 'ground' or another mass.
Appreciate that electricity will only flow (pass a current) when there are two connections at differing potential. With the a.c. mains, one of the connections is permanently established at 'ground' but in a vehicle there is normally no such reference for the vehicle body. If one wire of the inverter came in contact with the vehicle that would become the ground reference and then you would need to become in contact with that and also the other wire of the inverter in order to receive a shock. It would not be possible to inadvertantly create a situation where a vehicle could become alive from an inverter and injure a person.
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Follow Up By: Member - Cuppa - Tuesday, Jan 02, 2024 at 15:51

Tuesday, Jan 02, 2024 at 15:51
Allan, perhaps I have used the term 'live' incorrectly. I certainly recall the potential for a rescuer being electrocuted in the type of scenario I made reference to being a common topic of conversation & there being warning stickers folk used put on the exterior of their vehicles for that reason.

And the advice to minimise the length of the inverter 240v output cable to charger for that reason.

Maybe it was incorrect advice back then? If so it was advice that many folk accepted & built accordingly.
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Follow Up By: Allan B (Sunshine Coast) - Tuesday, Jan 02, 2024 at 16:10

Tuesday, Jan 02, 2024 at 16:10
Yes Cuppa, it would have been "incorrect advice back then" and it still is today. It is easy and common to generate erroneous expressions about electricity. It is after all, something of a Black Magic.
But it is probably good practice to keep all 230v leads to a minimum length.

In order to make a vehicle body 'live' with reference to ground it would be necessary to connect one of the inverter 230v wires to the chassis and bring the other paired wire out and connect it to a metal stake driven into the soil. Now you have a referenced pair at 230v and that would be dangerous.
Fooling around inside the vehicle with a couple of 'live' wires floating around is another matter.
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Reply By: greg b39 - Thursday, Jan 04, 2024 at 22:44

Thursday, Jan 04, 2024 at 22:44
Congratulations on your campervan purchase! It sounds like you've got a great setup with the second battery, solar power, and an AC/DC inverter. Generally, it's possible to charge the second battery using external power through the inverter, but it depends on the specifics of your current electrical setup.

To give you accurate advice, I'd need more details on your inverter's capacity, the type of charger you're considering, and the overall electrical system configuration. In some cases, an additional charging controller may be needed to regulate the charging process and protect your battery.

It's recommended to consult with a professional or someone experienced in campervan electrical systems to ensure a safe and efficient setup. Feel free to provide more details, and I'll do my best to guide you in the right direction!
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Follow Up By: RMD - Friday, Jan 05, 2024 at 07:40

Friday, Jan 05, 2024 at 07:40
greg b39
From what Leon told us we have worked out what his configuration is,
The inverter LEON has, DOES NOT HAVE A 240v AC input at all. So it can't be used from external power, ie 240vac! It only has a 12v input The inverters capacity is not the issue!
If you see the EXTERNAL POWER as ANOTHER battery of 12v, yes, that would make the inverter run inefficiently, to output 240vac to use with a charger to charge batteries. BUT he isn't even considering ANOTHER battery in addition to what he has got and the downside is that would have to be charged as well.

If considering the above, anyone would simply use a 240vac input battery charger to charge the battery! Why would you want to introduce losses and complexity to a simple issue?

Sorry but Best and Guiding isn't currently happening.
P.S. If you bother to magnify the picture which Leon provided it shows the Inverter is 1500W and Sine wave, that sort of explains the inverter capacity to me!
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Reply By: Allan B (Sunshine Coast) - Friday, Jan 05, 2024 at 12:31

Friday, Jan 05, 2024 at 12:31
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Hi Leon,
What you have appears to be rather basic. Your photo shows a battery and an inverter which takes 12vdc from the battery and outputs 230vac (as RMD said). The white cable obviously plugs into the inverter to take the 230v to who-knows-where. I can see no controller for solar input although it may be hidden. There is no provision to charge the battery from the 230v mains and you would need to add a suitable charger to achieve that.

But of more concern to me is that the installation is poor with the battery and inverter being apparently unrestrained, wiring floating around, and no fuses in sight. It really should receive attention from an electrician, at which time a charger could be properly installed. It may cost a few dollars but what price do put on your life or a fire?
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Allan

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Reply By: Keir & Marg - Friday, Jan 12, 2024 at 10:12

Friday, Jan 12, 2024 at 10:12
Do you know how your second battery gets charged from the car and from solar??? There are several ways to do the job. The 2nd battery may be wired through an isolation relay (controlled by the ignition) so that the 2nd battery is charged by the alternator when the car is running, but isolated when the engine is stopped, so that the car's main battery doesn't get drained when you are camping. The 2nd battery might be charged via a DC-DC charger which contains its own isolator (more expensive, but a much better way to charge the battery).
For solar, there should be a PWM or MPPT solar inverter fitted either to the panels, or close to the 2nd battery.
If there is a DC-DC charger, these usually have 2 inputs, one for 12V from the car and one from the solar panels. In this instance, the DC-DC charger contains the solar inverter inside the box, so you can feed unregulated solar panels to the DC-DC charger.
If you have a DC-DC charger, you can buy a correctly-sized 240/12V power supply and hook it up to the 12V input. Plug the power supply into the mains when its available, and the 2nd battery will get charged.
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