Battery W/ Suspend-To-RAM

**SuperMatty** · 03-07-2003, 12:08 AM

In August of this past year, I bought a new DIEHARD gold battery for my 98 Malibu. Keeping in mind that I've been using suspend-to-ram since June or so. Well, lately, I've gone out to start my car in the mornings to go to class and the battery has been completely drained.

I'm not quite sure...but it seems like suddenly my battery isn't able to sustain my computer in suspend-to-ram for more than like 12 hours. Has anyone had this happen to them? I took the car to the SEARS auto center to check my charging system and the battery, and they said everything checked out OK.

Now I don't really know, but my thought is, even if that SEARS DieHard battery is 90% shot, I'll bet that their tester will still say its OK so they avoid having to give as many warranty replacements. Is it possible that since it's been much colder here lately that the battery is limited in capacity? I don't know much about it, but I think I've read that batteries have a "cold resistance?"

**grandamp3** · 03-07-2003, 02:53 AM

By suspend to ram do you mean hibernate or do you mean standby? If you mean hibernate, I dont think it draws anymore power than if your computer is simply turned off. If you mean standby, then yes, your computer would draw power, but to my understanding, very very miniscule that you could probably leave it on a day or two. But anyway, answer that question for yourself and then you might check up a bit more. Also you might hook up a monitor to your carputer and then "suspend to ram" and see if it actually completes the process or if it rather hangs up and therefore draws full power.

**ShinkunoNamida** · 03-07-2003, 08:42 AM

suspend to ram is a type of standby .. hibernate actually does shut your computer off.

I've been using str for the past month or so with out any problem, I've left my car parked for a few days at a time. The opus supply that I'm using has a builtt in auto power off at 11v but there hasn't been a necessity.

What power supply are you using? DC-DC? Inverter? Unless you are using DC-DC STR is illadvised.. I'm also using an Epia800 system, so power requirements are absolutely minimal.

Batteries do behave less nicely in cold weather, it's been dancing in the 20s here dippy down to 0F at night time though..

Maybe I'm destroying my battery.. but I don't think it's a problem since it's not been dipping below the low power threshold of the low power protection on the psu (This is where I hope that it's working properly)

**SuperMatty** · 03-07-2003, 08:49 AM

I'm using the Keypower 250W DC-DC. and Yes I'm actually using suspend-to-ram, or standby as its sometimes referred to.

**Aaron Cake** · 03-07-2003, 09:46 AM

You need a deep cycle battery. Standard automotive starting batteries are not designed for cycle use. After a few cycles, the battery will be destroyed.

**SuperMatty** · 03-07-2003, 09:50 AM

LOL...well the idea is that I don't want to continue to have to jumpstart my battery

I saw Radio Shack sells a solar "trickle charger" that provides like 175 mA to your battery from the sun. That might help out a bit, possibly?

I think really the problem is, when I'm here at school I use my car to make short, low-speed trips and I don't think my battery ever is able to charge 100% becuase of that, coupled with my subs & amp which are drawing lots of current.

**ShinkunoNamida** · 03-07-2003, 01:06 PM

Originally posted by Aaron Cake
You need a deep cycle battery. Standard automotive starting batteries are not designed for cycle use. After a few cycles, the battery will be destroyed.

Aaron am I mistaken in assuming that with a deep cycle that my battery will run flat if one were to count on voltage protection to shutdown their computer?

**digitallexus** · 03-07-2003, 09:18 PM

The amount of power used during standby is mostly dependent on the type (DDR vs non) and amount of ram you have.

I have 512MB of PC2700 DDR and it draws ~297mA while in standby. That's at 5v though. At the 12 input, only 124mA is being consumed. (ignoring DC-DC conversion effenciency).

So 2970 mAH or 2.97 Amp-Hours of power is used for each 24 hour period.

Keeping a battery charged depends a lot on how long you drive the car during the week to replace the power used.

A solar panel sounds like a great way to supplement power during the day. For those of us living in the Seattle area though, this probably won't prove to useful :-)

Assuming I can't keep a battery charged using the alternator, I also considered using a easily removable laptop type battery that I could charge in the house. My Dell laptop batterys for instance are 66 Whr'sand would last about 2 days.

You could also create a complex system where during your waking hours the computer is held in standby mode. At the end of your day, the shutdown controller could automatically pull the computer out of standby, and shut it down via hibernate. In the morning it could start the machine backup up and then drop it into standby, ready for a days worth of instant access.

Of course this depends a lot on how much power the computer uses while fully on. The two short state changes would of course use a lot more power in the full-on mode rather than standby but are very short.

Lets say that power on usage requires 3A at 12v, 1 minute of time would require only 50mA. Going into and out of hibernate shouldn't take more than 30sec each so a total of 100mA would be used.

Now assume that you won't use the car for a 12 hour period every day. 12 hours of standby requires 1500mA. The state changes only consume 100mA, so 1400mA are saved each day!
In this example, we have doubled the number of days from 2 to 4 on a single charge of the battery.

This technique combined with a deep cycle battery that is charged with the alternator might allow even seldom driven cars able to sustain a computer indefinitely.

**SuperMatty** · 03-08-2003, 03:22 PM

I really am considering adding a second, deep cycle battery. My concern is if this wil prove to be too much for a 105 amp alternator though.

**Aaron Cake** · 03-10-2003, 09:32 AM

A deep cycle will probably still run dead, but will be able to handle the cycle use.

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