/ Charging leisure battery query

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markalmack 07 Jan 2020

My camper is parked in the shade all day and the leisure battery is slowly draining. Im wanting to connect a mains charger to it, but am a bit worried about damaging the solar controller. Should i disconnect this first, or am i worrying about nothing? 

Similarly i am thinking about having a switch (or vsr) to connect the leisure battery to the van battery when driving to do the same. Would this be a problem?

Its an epever mppt beast, but it doesn't say owt in the instructions about connecting an external charger. It does say i need to disconnect the solar before disconnecting the battery which would be a pain, so would rather not.

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Denzil 07 Jan 2020
In reply to markalmack: should be no problem leaving the solar charger connected when you have the mains charger connected. Similarly no problem if you have a voltage sensitive relay to connect the two batteries. Reason for disconnecting the solar panel (if it has no proper solar charge controller along with the panel) is that without a proper controller the voltage from the panel could go up to 30V - which could damage other components.

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Hooo 07 Jan 2020
In reply to markalmack:

I have an ePever MPPT controller. It's no problem charging the battery with it still connected, it's designed to cope. A standard van setup will have a VSR that connects the leisure battery to the alternator when the engine is running, so I am effectively putting the leisure battery on charge every time I start the engine.

I've never worried about disconnecting the solar panel before the battery, but not a bad idea. But if you disconnect the solar, always cover the panel first so that it is not generating.

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Darron 08 Jan 2020
In reply to markalmack:

I’m no expert and don’t know your setup but In winter I just hookup van via normal 240v for 24hours once a month. Have a friend who keeps her van permanently hooked up when at home. CC club have various tech sheets online that may be of help?

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Ciro 08 Jan 2020
In reply to Hooo:

> I've never worried about disconnecting the solar panel before the battery, but not a bad idea. But if you disconnect the solar, always cover the panel first so that it is not generating.

I've never worried about covering the panel before disconnecting, just make sure the cable ends are insulated before I put them down.

I never use to bother about disconnecting the panel before the battery either - never seemed to do any harm to my old controller or anything running off it, however when I updated my system recently to LiFePO4, I had a fit of sensibility and installed a DC circuit breaker - no excuse for being lazy that way 🙂

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George_Surf 08 Jan 2020
In reply to markalmack:

Anyone know if it’s ok to have two separate solar panels rigged to two separate charge controllers plugged in to the same 12v battery? I assume it’s like when you’re alternator is on; so it’s absolutely fine?

(It would be useful if you had a fixed panel on the roof and a portable panel that you get out when you’re parked up).  

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Hooo 08 Jan 2020
In reply to George_Surf:

No problem doing that. If you have a smart solar controller that does multi stage charging it might get confused. All this would mean is that you battery might only charge to 95% or so, it won't do any damage.

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Hooo 08 Jan 2020
In reply to Ciro:

It's more the re-connecting I worry about. Fiddling around in a little cupboard trying to get a 6mm2 cable into a small terminal is a bit worrying when said cable could deliver 8A or so.

Although, as you say it's no problem if you're careful. I once reconnected it all and got out of the van only to see that the cover had blown away and the panel was in full sun

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Ciro 15 Jan 2020
In reply to Hooo:

> It's more the re-connecting I worry about. Fiddling around in a little cupboard trying to get a 6mm2 cable into a small terminal is a bit worrying when said cable could deliver 8A or so.

> Although, as you say it's no problem if you're careful. I once reconnected it all and got out of the van only to see that the cover had blown away and the panel was in full sun

It might be capable of delivering 8A, but unless you've got multiple panels in series, the max voltage will be about 40 - 50v... 48V DC is the upper limit of what's considered safe for DC. You'd get a nasty shock if you stuck them in your mouth, but through dry skin you'd be lucky to feel a tingle.

The only real danger would be if you connected it next to the vent of a charging lead acid battery and managed to blow it up with the spark - but that could just add easily happen when disconnecting first. Best avoided by not having your LB & charge controller in a dodgy configuration.

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