# Charging Deep cycle while running LED lights



## titan1

I have a couple questions, mainly regarding safety, about charging a battery that I use to run between 1-6 12v LEDs inside of a tent. I believe the battery is just a normal deep cycle/starting marine battery.

In the past, I would run the battery down to roughly 40% or so and then use a regular battery charger - 12v 10 amp (then manually switch to 2 amp) to recharge using a generator. 

I was thinking about permanently connecting a battery charger/maintainer to the battery so whenever the generator is running, it would be recharging. 

My question is what kind of charger would be best? Something like a Noco Genius 3.5 amp? 

Also, can I still use the LED lights while the generator is running and it's charging? The pull on the battery from the lights would be between 1-5 amps depending how many would be on. Is it as simple as the charger would cover 3.5 amps and the battery would provide the rest?

Also worried about gas build up. The battery is in a plastic battery box. Do I need to leave it uncovered while charging? The tent is large - 500 sq ft +. Is that enough ventilation? What condition do I need to avoid?

Thanks for the help!


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## titan1

Just thought I would bump this to see if anyone had any comments. I head up to the mountains fairly soon and just want to make sure I am being safe. Not really sure how to research this otherwise. 
Thanks!


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## terjee

Couple of quickies, hope it's not too late, I only noticed this thread just now.

First of, this is probably fine, but keep reading. 

There's a couple of thing you could check out though. A charger could theoretically have a drain on the battery if you leave it connected to the battery, while the charger doesn't have power. It's usually minor, but worth checking out if you have some spare time.

Every lead acid charger I've checked out is happy with some load on the battery, but chargers are getting smarter, and it's hard to guarantee fully that there isn't a charger out there that'd be confused by it.

Which charger is best is hard to answer. Most important factors are that it'll feed the battery at a comfortable rate for the battery, and that it monitors the voltage and doesn't overcharge. 3.5A sounds low for a large battery, but that's not a problem other than charge rate.

Normally you're right about charging while using. Imagine a bucket with a hole in the bottom, you're filling the bucket with 3A, draining it at 1-5A at the same time. Level of water in the bucket corresponds to both state of charge and voltage of the battery.

If the charger is smart, it might trigger if it sees the battery voltage drop down while charging it, if you're putting in 3A and draining out 5A, but I'd expect that to be an error you can clear, reduce load, and charge again, possibly having to reconnect the charger to have it restart.

Nothing about what's said so far is anything I'd be concerned with if it was my stuff, but it's always scarier to give advice to others. ;-)

Do remember to fuse things (at least into and out of the battery), and check for heating etc.

Venting is the hardest to answer, because I don't have enough info. It depends on both size and type of the battery. Risk of gassing is highest if the load is high (relative to the battery) or if you're overcharging it. Sealed types are often safer than "normal" flooded types.

Based on it being marine, there's a good chance it's a large flooded. If that's the case, then 3A is nothing load-wise, which is good. I wouldn't seal it or cover it up when in use, just to be on the safe side.

Conditions to avoid are over current (unlikely, but check spec of the battery, especially if not large).

Safety-proof goes like this:

The risks are overcurrent, overvoltage, and undervoltage.

For overcurrent, you fuse. If the battery can handle 100A continuous, and your load is 1-5A, use a 7-10A fuse for example. Plenty of margin, problem solved.

For undervoltage, it seems like you already have a solution? (Since you stop at 40%).

For overvoltage, use a charger that terminates at a given voltage, problem solved.

All the major risks mitigated. 

Two quick but important additions:

During charge, a charger could push as much as 14.4V. The LEDs are unlikely to see the full voltage due to voltage sag across the wires etc, but they might see more than 12V. That could also lead to some extra current drain. Worth keeping in mind.

Age of the battery is the bit X-factor. No battery lasts forever, and certainly no lead acid battery. Good to be mindful of heating, any signs of gassing, and so on. If in doubt, consider replacing it or having it checked out. Some flooded types of batteries need the fluid levels topped up (battery water).

To sum up:
I don't know the battery, so I can't say "go eighth ahead, I promise it'll be just fine".
But there's nothing I see as a red flag with regards to wanting to leave the charger connected, or charging and using at the same time. It's almost always fine.


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## titan1

Wow! I really appreciate the info. Sounds like I had the right idea, but just wanted someone to double check me.

I do have the lights fused (10 amp) and will charge/discharge uncovered. 
The battery is only a year old
I bought it straight from a distributor so it doesn't have markings, but I was told it's a group 27 marine/starting battery. I would have bought a dedicated deep cycle, but the deal was way too good to pass up.

After some more research, I found the Noco 7200. So 7.2 amps vs the 3.5 of the lower end model. I "chatted" with a tech on their website and he said no problem charging while running and the charger will not overcharge in either circumstance. It also has a 5 amp "supply" mode that could actually just run the lights while the generator is running, but I couldn't figure out if it could possibly overcharge in this mode.

The charger also has a quick disconnect wiring harness. So I can easily plug it in when needed if there is a discharge issue while not running.

Again, I really appreciate the hep and advice. 

Thanks


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## terjee

If possible, I'd fuse the charger as well. Basically fuse any wire going into or out of the battery, as close to the battery as possible.
The reasoning is that even though the charger could deliver "only" 7.2A, the battery could possibly shove 1000A into those same wires if they short, or anything else unforeseen happens (rodent in tent?).


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## titan1

Good call, I'll throw another fuse on those connections that come with the charger. We do get rodents in there...I never thought about it causing and issue like that.


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## Str8stroke

If you have have never experienced a 12 volt deep cycle battery vent, I can tell you it is a freaking mess! A dangerous mess! I had a battery less than 2 years old vent in my garage. The fumes fill my entire house! It burned my eyes when I went out to unplug the charger (trickle). I now view them differently from a safety stand point. 
Don't believe me, search images of 12 volt batteries exploding. That's a real eye opener. So just be safe.


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## titan1

Did you figure out what caused your issue?


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## HarryN

Most of the issues can be avoided if you use a charger with at least 3 stage charging, and always put them in a battery box or some kind for protection of the wires, battery, and you.

As far as venting, most lead acid batteries (all of them AFAIK) need to be vented to the outside, not inside of your vehicle or tent. There is nearly always some H2 gas created during the charge cycle, which also carries some of the acid electrolyte along with it. It isn't a lot of material, but you really don't want this inside of your vehicle, tent, or lungs.

Even a 1/4 inch tube is usually enough to carry this to the outside.

The H2 is typically what causes lead acid battery events.

RVs routinely are setup to charge and discharge from battery banks simultaneously if that helps.


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## titan1

When I say tent...I'm talking about 650 sq feet of tent. Plus quite a bit of ventilation from the door opening and closing. Material is also breathable. I assume this would be enough?

So from what I understand - charge uncovered. Use covered by battery box. Correct?


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## broadgage

Modern deep cycle batteries are very safe, accidents have occurred but are rare.
I would be happy to have one in a tent.

Charging the battery whilst supplying lamps is entirely doable, remember that these batteries are often used on motorboats when internal or navigation lights are routinely used whilst motoring.
Two caveats.
Firstly make certain that the LED lamps are suitable for use at up to 14 volts. If they are intended for vehicle or marine use they should be fine. If however the lamps are intended to be line powered via a 12 volt PSU with a regulated output, then 14 volts might kill them.
Secondly, choose the battery charger with care ! avoid anything claimed to be 3 stage, multi stage, or smart.
You need a simple single stage, constant voltage charger with a regulated 13.8 volt output, sometimes called a float charger.

A 3 stage or smart charger can become confused by trying to charge a battery with a load connected. These chargers normally work as follows.
Stage one---------constant current until the voltage reaches 14.4 volts.
Stage two---------constant voltage at 14.4 volts until the current drops to say 1 amp.
Stage three-------After the current drops to less than 1 amp, the constant voltage charge is maintained for say 2 hours.
Stage four--------after the 2 hours has elapsed, the charge voltage is reduced to 13.7 volts, which may be maintained indefinitely.

This works fine for a battery not connected to a load.
Adding a load may result in overcharging. If the load is 1 amp, then in stage two, the charger output will never drop below 1 amp, and the 14.4 volt charge will continue indefinitely. This will overcharge the battery and if long continued might even be dangerous.
Multi stage chargers are also not ideal for use with a generator or other intermittent supply. Each time the generator is started, the charge cycle starts again even if the battery is full. Stage one will be over in a minute or so with a full battery, all good. Stage two will likewise be completed rapidly, all good. Stage three however will still run for the pre-set time of 2 hours, not good for a battery already fully charged.
Occasional overcharging due to the repeating of the charge cycle should not matter much, it is comparable to the odd utility failure at home causing a charger to re-start. If however if it occurs frequently due to the starting and stopping of a generator then significant over charging may result.


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