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Discussion Starter #1
Hello all...i have a question which i hope anybody with experience can help me with...
I do camping and offroading a lot. I have a lot of gadgets which i plug in the cigarette lighter. This is including a Power Inverter (150 Watt capacity) which converts 12V DC to 220V AC. It has an auto shutdown feature when the voltage is too low (below 10V).
My question is: if I put an extra battery (same size as the stock battery... I have a Suzuki Jimny 2010 model) and put them in series together....will this avoid the voltage dropping to below 10V?
Can my alternator handle the extra battery?
I do not have any experience with batteries I'm afraid...:(
 

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The LAST thing you want to do is put two batteries in series - you'll burn a lot of stuff up if you do.

Parallel is what you probably mean - positive to positive, negative to negative - this can be done, but you'd probably be better off with some sort of isolator between the two to avoid running the start battery down to the point where you can't get a start.

You'd also probably be better off with some sort of deep cycle or possibly a marine battery as the second battery - automotive batteries are designed for cranking or starting services not deep discharges, and will fail rapidly if subjected to this sort of service.
 

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Discussion Starter #3
thanks for the quick reply fordem!
hehe that's what i mean...parallel...
Marine battery? could i put it in parallel with the stock battery (as long as both are the same voltage)? do u think my alternator can handle both at the same time?

i'm using my gadgets while i'm running my engine so the stock battery will not drain out...or will it?
 

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Let's start by drawing up a power budget - make a list of your gadgets, the amount of power they draw and an approximation of the number of hours per day you'll be using them - then give us an idea of how much driving you're going to be doing - that's the only way we'll know what's what.
 

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Discussion Starter #5
ok...list of gadgets:

GPS (don't know power consumption) - 5 hours
Mobile/ Iphone charger (5Amps) - 2 hours
Camping lights (24Watts) - 4 hours
Kettle (100Watts) - 1 hour
Power Inverter (150 Watts) - 4 hours
Spotlights (i will install these in the future) x2 (50 watts each) - 1 hour

I am driving on average about 5 hours a day...
 

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ok...list of gadgets:

GPS (don't know power consumption) - 5 hours
Mobile/ Iphone charger (5Amps) - 2 hours
Camping lights (24Watts) - 4 hours
Kettle (100Watts) - 1 hour
Power Inverter (150 Watts) - 4 hours
Spotlights (i will install these in the future) x2 (50 watts each) - 1 hour

I am driving on average about 5 hours a day...
You need to know actual power consumption, not rated max output. A phone charger is not going to pull 5 amps at 12 volts, you can probably run a phone off 7.4v @ 150 mah, so at 12 volts, probably less than 50 mah x 5 hours, 250 milliamps or .25 amps.


your GPS probably the same as the phone.

Camp lights. 24 watts = 2amps @ 12 volts that's 8 amps over 4 hours.
Kettle 100 watts = 8.3 amps @ 12 volts
Power inverter is supplying the power to everything, not actually using 150 watts, just supplying UP to 150 watts of AC power from your DC power source.
spot lights 100 watts= 8.3 amps @ 12 volts.

so if everything is running for the durration you indicated you'll have about 22 amps from your 12 volt battery, or about 740 watts of power over the course of 4 hours. most of that will be used in the one hour your spots and kettle are on. . A standard small 45 amp-hour battery should easily handle it and the alternator should easily recharge your battery, but when camping you should always run your gear off a backup battery if you are using it with the vehicle turned off. You shouldn't draw more than 4 or 5 amps per hour off a standard 45 amp hour lead acid battery, so a higher discharge capable battery would be better to use.

If you plan on getting spotlights, you'll need to upgrade your inverter. You have 150 watts of power available, and if you try to run your kettle and your two spots, you'll blow the inverter. It will handle the kettle and the camplights, or the camplights and the spots, but not the kettle and the spots simultaneously.
 

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Ok.

GPS will be no more than 1A and I assume the 5 hrs/day will be whilst you're driving, I think we can safely ignore that, if you don't already have a car charger for your phone, get one, and also charge the phone whilst driving (and again, we'll ignore that).

Camping lights - get yourself some LED lamp bars that run off of 12V - those are low current (the ones I have actually run off of 3 AA batteries and the battery last for forever)

Kettle - 100W - that's a pretty low wattage kettle, but I assume you know what you have, and also that this is what you're using the inverter for, 1hr/day - what else are you using the inverter for to account for the remaining 3hr/day?

By the way 12V kettles do exist, and they're not expensive. If possible eliminate the inverter (as a rule they are not particularly efficient and in my experience not that reliable), so if we can run the kettle directly at 12V we'll save some power there, and maybe just plug the kettle in and leave the engine idling for 10~15 mins after you park (or before you leave).

Just so that you understand where I'm going with this...

If we can reduce the amount of energy you're taking from the battery whilst the engine is off to the bare minimum, we might be able to do it all with the standard battery, and so far, I think we're doing pretty good.

Take a look in the back of your Jimny manual, it should tell you what the alternator output is.
 

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Discussion Starter #8
hey guys sorry for the confusion...
i am running the kettle and camp lights all from the 12V cigarette lighter...not from the inverter.
i only use the inverter for running my laptop.
i plan to directly connect the spotlights to the battery...not from the inverter.
ok fordem, i will check the power output of my alternator from the manual...
 

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like fordem said a deep cycle or marine battery for your second battery and i would recomend that you look into a dual battery system they dont let your cranking battery to be used while the key is in the off position but you can still run your camping appliances every one i know has put extra sockets in there car that run off the second battery. each dual battery kit is different so look for the one that best suits you.
 

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See if you can get yourself a car adapter for the laptop and eliminate the inverter altogether - additionally - consider running the laptop off of it's internal battery and plug it to charge whilst you're driving.

What's the power consumption on the laptop like - they range from 30W on a netbook to as much as 120~150W on the larger "desktop replacements". 65W seems average for most 13" systems.

24 watts in 12V camplights is 2a x 4 hrs = 8aH
a 65w laptop from 12V is roughly 6a x 4 hrs = 24aH

You're looking at 32aH from a 45aH battery, not good at all. The rule of thumb if you want long battery life from a lead acid battery is not to discharge it by more than 20~25% of it's capacity at any one time, and that is for deep cycle batteries - automotive starting batteries have thinner plates and are not designed for this type of "cycling" service, so they deteriorate even faster.

Using the equipment you've outlined a marine or deepcycle battery of 150aH capacity will do what you need - but - I believe that for the same (or less) expenditure as you'd incur with a battery & isolator, you could take a more energy conservative approach, and organise as much of the energy consumption to coincide with the time of production (the period when you'll be running the engine) and you'd get by without needing an additional battery.

Very briefly ...

Lead acid batteries use plates made of lead suspended in sulphuric acid - the plates are usually made in the form of a grid into which a "spongy" lead paste is forced.

Automotive batteries are designed for high current discharges (anywhere from 600~1600A) for short periods of time (10~30 seconds) to start the engines after which they are immediately recharged - they use larger numbers of thinner plates.

Deep cycle batteries are designed for what is known as "cycling" service - to supply smaller currents (smaller than automotive cranking currents) for longer periods, these are found in many applications - solar-electric power, camping, etc. - these have smaller numbers of thicker plates.

With each discharge/recharge cycle, the plates expand & contract, and with the thinner plates used in automotive batteries. there is some shedding of the active lead paste, and this is what leads to the rapid deterioration if used in cycling service.

Marine batteries are a compromise between the two - designed with thicker plates to allow some cycling service - use of cabin & navigational lights etc., whilst the vessel is moored and also cranking to start the engines when necessary.
 

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dragging your other topic into this one. the 200AH battery should be ok for your intended load. If it's a deep cycle battery it should be able to handle a 20% discharge rate without a problem, and that would give you around 40 amps or 480 watts.


Like fordem was saying, a stock lead acid automotive cranking battery isn't designed for high discharge over prolonged periods of time and it will deteriorate rappidly if over tasked.

A small stock battery is about 40-60AH and the maximum recommended continuous discharge rate on an OEM spec Lead Acid Battery is about 10% of capacity. 4-6 amps, or 48-64 watts.
 

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Discussion Starter #12
guys thank you for the tons of information...i've really learned a lot from this discussion.
ok, please correct me if i'm wrong...this is what i understood:

1. if i'm running my engine while using my gadgets, i will be fine...no need for an additional battery.

2. if i want to run my gadgets when my engine is off...i would need an additional battery (deep cycle) with an isolator. Roughly, how much would be the cost to install deep cycle battery plus isolator?

3. i would be fine with my alternator (i couldn't find the power output of my alternator from the manual).

is this about right?
 

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the older suzuki alternators put out about 50amps. The newer ones I'm sure are going to be at least 60-75 amps which would be adequate.

Battery Isolator Controller [BR-31-0000131000] - $77.42 : MC Camping Supplies, Your Complete Camping Source

for a deep cycle battery that also will double as a cranking battery, you can get an Optima yellow top battery, or one of the Optima blue tops with light grey body. DOn't get a blue top with the dark grey body. Those are for cranking only and not for cycling. A good deep cycle battery will set you back between 150 and 200 dollars U.S.
 

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See my comments in green

guys thank you for the tons of information...i've really learned a lot from this discussion.
ok, please correct me if i'm wrong...this is what i understood:

1. if i'm running my engine while using my gadgets, i will be fine...no need for an additional battery.

The gadgets you've outlined - yes.

2. if i want to run my gadgets when my engine is off...i would need an additional battery (deep cycle) with an isolator. Roughly, how much would be the cost to install deep cycle battery plus isolator?

3. i would be fine with my alternator (i couldn't find the power output of my alternator from the manual).

I would guess at around 60~65A, I think you should be fine.

is this about right?
 

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Discussion Starter #15
ok, thanks a million guys. this info gives me peace of mind when i'm camping...
if i add more gadgets, like a refrigerator...summer is fast approaching. I'm in United Arab Emirates...summer temperatures could reach 50 deg C. Having a cold drink is paradise. I would add a deep cycle battery soon.
 

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You'll need to watch it with that refrigerator - try to keep it out of the sun, and make sure air can circulate around it rather than leaving it in a closed vehicle - if necessary rig some sort of vent system.

There used to be solar powered fans that you could put at the top edge of a window and wind it up to secure them - the hotter the day, the more air they moved - haven't seen then in a while though.

The reason behind the suggestion is this - a closed vehicle is like a glasshouse and traps heat - if you don't vent that heat, the refrigerator runs for longer periods and can seriously deplete a battery.

Edit.

I googled a bit and found some of the solar powered vent fans - seems they don't work too well ....

Depending on your choice of refrigerator it may have it's own fan or perhaps you can rig it with a 12v computer fan and duct the air flow.
 

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A true deep-discharge battery design will work best for your application. The standard BCI group 24 battery size is about 75AH. The larger Group 27 battery size is about 100AH. Larger than that, you'll likely have to use two batteries. For the longest life, try to keep from frequently/regularly discharging a wet-cell battery below 50% of it's AH rating. But an AGM battery will survive really deep discharges very well. If you really need 200+ AH, you could consider connecting two 6V "golf-cart" batteries in series. They're 220AH and putting them in series will give you the 12V you need.

A simple marine-type battery combiner switch could work for paralleling your batteries. You would disconnect the camping battery before use and re-connect just before starting the engine. The few seconds of paralleling a discharged and charged battery would not be a problem and would be easiest on the battery combiner switch. Once started, the alternator would charge both as needed.
 

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Discussion Starter #19
hi merlin...in the set-up you mentioned using a battery combiner switch (like a manual switch?). So i could eliminate buying an isolator to save cost?
 

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I use a very heavy-duty BlueSea #3002 in my motorhome, but I've got a HUGE (300 lb) battery bank. I believe that one Harbor Freight #66789 would work for you, as long as you keep the current through it to a few tens of amperes.

For safety, be sure to double-insulate any wire connected to a battery (+) terminal until it gets to a fuse, and keep it short in any case. If it shorts to chassis, the current from the battery would be unlimited.

The worst moments for any switch (or relay) are opening and closing with high current. So, open and close (operate) the switch only when there's no current flowing -- engine NOT running, and camping battery not supplying any load current to external devices. The switch can carry a lot of current once it's fully mated, but not-near-so-much while it's opening and closing.

Edit: Note that the switch terminals are very exposed. If you put this switch in the (+) side, be SURE to protect all the conductors, including the exposed nuts, posts and terminals, from ever coming in contact with grounded metal. The available short-circuit current from even a small automotive battery could be 1000A+. I also see no reason not to put the switch in the grounded (-) leg, if you prefer. I'm thinking that a 100A fuse (perhaps a MAXI), would be about right for a 65A (guessing) alternator. On my 90's Samurai, I'd have to reinforce the skinny little black chassis-ground wire from the Battery (-) to the chassis. Billjohn likes to add flexible ground braid from near the starter/bellhousing to the chassis, and I really like that idea.
 
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