Power tanks. Which its best?

[Star Hunter]

I'm hunting around for a 12VDC power tank (Truck crank jumper type perhaps) to power up to four Firefly dew heaters and two non goto mounts, to last 8-10 hrs use. Anyone suggestions?

[LewisM]

I got a 44AH 'V8 engine" jump starter pack from Super Cheap auto - cost was very reasonable (weight is about 15kg, so be aware of that) - 2 cig lighter sockets, 1 USB power socket. I bought a cig lighter cable splitter from Jaycar, and now have 6 sockets. I run 2 dew heaters, a CCD camera and a mount and laptop (through inverter). Does not even lose 1 bar of the charge meter after a full night (these are designed to be recharged after 3 jump starts of V8 engines, so, yeah, it's pretty gutsy). My mate Phil uses similar, and he powers a Takahashi EM-400 mount all night, and RARELY recharges it.

My prior 9AH battery pack that worked absolutely fine in QLD just could not handle low temperatures of Canberra, and would start beeping after about 4 hours - that is going from fresh recharge.

[rrussell1962]

By coincidence I was down at Repco this morning and they had a 44Ah jump starter on special - something like 40% off I think, maybe worth a look at a store near you. Having said that I don't know how their discounted price compares with SCA's regular price.

[LewisM]

Mine was $201 at SCA a little while ago now.

[glend]

In my experience, the car jump start units do not last very long. They may handle your load but they designed for high amp output in short bursts and not long sustained deep cycling. If you let them sit they will lose their charge, and once that happens they cannot recover. I won't use them anymore, preferring deep cycle batteries for dark site work. I use a 44ah for mount power and have a 100ah for dew heaters, laptop inverter, camera cooling, etc. Does not take long to recharge next morning with a solar panel, and they have lasted for years with no sign of deteriouration. They are heavy buggers, especially the 100ah, but they last. I must admit they do double duty, at home they sit in the observatory on float.
Read the fine print on thise car jump start packs, most of them have batteries with less than 20ah inside.

[casstony]

Perhaps two ~40Ah deep cycle gel batteries would do and avoid the 100Ah back breaker?

I use a 38Ah deep cycle battery for a goto mount and that battery is already quite heavy.

The newer LiFePo4 lithium batteries would be great for weight saving but they're expensive; I avoid the cheaper lithium batteries as I'm worried about them catching fire.

[LewisM]

I dunno - the 9AH I still have is going on 8 years now. Seems OK to me. Just cold-sensitive.

[Kunama]

Most of the smaller Jumper Packs have an 18AHr sealed lead acid battery inside. The Repco/SCA 44 Ah is a nice pack at a good price.

I have just switched to using a 16 Amp hour LiFePO4 Kit by DryPower, very light at 2.2Kg but a tad pricey at $350.... but it does have a benefit that I will be able to make a bracket so it can ride shotgun on the mount so no cable for people to trip on....

[issdaol]

I have a Repco 44AH battery pack......inside is an AGM battery......I have used it for running my fans, EM400 Mount and power to IPAD for 3-4 nights without needing to recharge.

Yes if you let them sit for ages ( I'm talking a fairly long time) they might die.....but for regular scope use thats not usually the case.

Deep Cycle batteries can also suffer the same problem .....but generally not to the same degree so you will get better life but you are definitely not immune.

Now days the best thing to do is as Matt has done and buy a good quality LiFePO4 battery and wire it up yourself.

Or if you don't want to wire it up yourself buy one of these.....

http://www.arkcorp.com.au/c/37/arkpak-portable-power