Battery Selection

I need to run my laptop for many hours and in a mobile state; i.e. no AC Power available not car available.

I have a Enercel AC/12VDC to laptop power block cord.

What is the best battery to use with this other than a full size car battery.

I have been looking at closed cell 12v 18AHr batteris as a possible choice. not sure is these are deep discharge. Or maybe a motorcycle battery.

Suggestions please.

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Reply to
OldGuy
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A spill resistant 12V lead-acid battery (eg AGM or gel-electrolyte construnction) would be compatible with that charger, and more conveniently portable.

there's probably a compatible lithium battery too, but I don't know the detaqils of that laptop charger or which lithum battery to reccomend, but, it would likely be more portable than the equivalently capable lead-acid battery..

check with the maker, some are designed for portable devices others for backup power.

A motorcycle battery is not spill resistant, not designed for deep discharge either. sulphuric acid fumes/seepage from that battery will destroy cotton etc.

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umop apisdn
Reply to
Jasen Betts

The SLA cells are designed to deliver power and is a much better choice than a car battery which is designed to deliver cranking current. You might also consider a honking great string of NiMh cells in battery holders. This might have an advantage in that you could reduce the amount of them you have to lug around if you only need to work for an hour or so.

Reply to
David Eather

If you have the proper charger then the best would be lithium ion batteries. They pack the most power, size and weight wise, of any commonly available consumer battery. Maybe you could get some of the batteries that power your laptop and that way you would have the proper charger available. Power your laptop with the power block while changing batteries, that way you won't lose very much power in the power block since it will only be used during battery swaps. So use one small battery to supply power to the power block because it is only used briefly. If you can't swap batteries for whatever reason then find a lithium ion battery to power the power block. They are now available as substitutes for motorcycle batteries. I know a few guys who have ditched their old lead acid motorcycle batteries for lithium ones because they are lighter. As if they could really tell the difference when riding. Eric

Reply to
etpm

One thing you can experiment with at home is to turn up the power-saving settings in the OS, get rid of programs that run in the background, etc, to maximize the runtime on the laptop's internal battery. If you don't need WiFi, and you have the "WiFi off" switch on the outside of the laptop, use it. This will help reduce the size of the external battery you need.

Do you know what the DC output capacity of either the Enercel or the original adapter that came with the laptop is? This can help you decide how big of an external battery you need.

A lot of recent Dell laptops come with 60 W power adapters; some of the "big" ones come with 90 W adapters. The laptop doesn't need this much power all the time, unless you are doing something compute intensive, like rendering HD video. I haven't measured but I would guess that a modern-ish laptop would "idle" in the 15 to 20 W range (screen backlight on, HDD spinning), before power saving features kicked in. This is around 1.8 A at 12 V, after allowing for a little loss in the adapter.

A "gel cell" or AGM battery, with whatever capacity you need to meet your run time requirements. This can range from the ones that go in an alarm system or small UPS (5 to 12 Ah or so) all the way up to ones that are the same size as a car battery.

Keep in mind that the amp-hour rating is usually over a period of 20 hours. That 18 amp-hour battery will give you 0.9 amps continuously for

20 hours. It's not quite linear; if you take 1.8 amps, you'll get a little bit less than 10 hours, and if you take 3.6 amps, you'll get rather less than 5 hours.

They are.

No. These will be designed for starting (short bursts of very high current, then immediate recharge) rather than deep-cycle use (lower current but over a long period of time).

Other advice...

Charge the laptop's internal battery all the way at home before setting forth. That way, all the juice from the external battery goes to running the laptop, and not to charging its internal battery. This also gives you some margin if you manage to run down the external battery.

Use a fuse between the external battery and the input to the Enercel charger.

Depending on how much battery capacity you need, one of the "jump start" boxes might do what you want. These have a battery packaged up with jumper cables; if you look around you can find one with a cigarette lighter socket already on it. It will also come with a (not very good) charger for use at home. The trouble here is that these tend not to list the amp-hour capacity of the battery; they give some wildly inflated claim about how many cranking amps it can deliver. You can kind of tell by weight, but the only way to know for sure is to take the thing apart and look.

Think about how you will charge the external battery when you get home. Connecting it to a car while you drive around isn't actually a horrible idea; the car's electrical system is *designed* to charge a lead-acid battery, although it may not get a sealed battery to 100% charge. A "dumb" high-current car battery charger is probably not a good idea; its voltage output will be too high for the sealed battery. (High current means more than about 20% of the amp-hour rating; for an 18 amp-hour battery, that's more than 3.6 amps.) A "smart" and lower-current car battery charger can work OK. The deluxe way is to get a charger specifically made for sealed batteries.

Charge the external battery as soon as you can once power is available again. If it has to sit for a day or two before getting recharged, OK. Even a week isn't too bad, but a couple of months is a bad idea.

If you're going to do this a lot, and your laptop has a hard drive, it may pay to replace it with a solid-state drive. They aren't cheap, but their power consumption is lower.

If it's something you can do on a smartphone or tablet instead, you might consider that. Full-size Bluetooth keyboards are available if you can't deal with the tiny on-screen keys on a phone.

Matt Roberds

Reply to
mroberds

First thing, consider the energy-save options on your laptop. Finding a power-stingy model or making power-management settings properly can give you a big boost. You might even consider buying a longer-battery-life laptop or tablet, it'd be easier than lugging lead/acid outboard batteries.

Second, many laptops can hotswap batteries (and the energy in an expensive Li-ion laptop battery is greater than an equivalent weight of lead/acid motorcycle battery). A vest with four pockets, and a laptop with 5 hour battery life, gives you better than 24 hours before you need recharging. No dangling cables on the laptop, this way.

If you do need to lug batteries, find a marine supplier and get a battery box with sling (the box will protect the battery from bumps and the sling will give you a handle). Marine 'deep-cycle' batteries are pretty rugged, but if it might tip over, you'll be better off with sealed lead-acid.

Reply to
whit3rd

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