A reminder about charging your PowerTanks

[cantharis]

A free battery is generally a "good thing". Use it till it goes belly-up....then get your deep cycle one from any decent chandler or alternative energy supplier (they are also used with PV arrays). Google is your friend....

Or a caravan equipment supplier.

[bluesman81]

Thinking about getting one of these while they're on offer - 5in1 Jumpstarter with Digital Air Compressor : InCar Battery Chargers and Compressors : Maplin

Maybe useful for people with dead powertanks

I got one of these when my SW powertank failed. Wish I had never bothered, left it on its initial charge for 24 hours and took out the next night and it lasted about 35mins running my NEQ6, dew controller and laptop (via a 12v laptop adapter). Took it back to maplins and the replacement was the same. Then changed it to the 3in1 system and it is perfect. Its also £24.99. Brilliant, wish i had got this one first.

[Mr TamiyaCowboy]

got myself a maplins 3-1 ( blue label ) jumpstarter.

works fine, but am going to take the jumpleads off

and mount a 4x cigar adaptor to the case,

an internal fuse to the adapter will then give me 5x 12v power outlets.

i also pulled the rear case of my pack to check what type of cell was mounted.

i can say they have now changed the cell units to a spiral wound battery.

mine is a 9ah 12v spiral wind cell pack ( yellow in color) and nothing like the standard gray /black rectangle packs.

after charging i read 13.5v on the meter.

am now looking around to find a decent marine 12v 21ah pack to fit inside the maplin case.

other places to find these 12v low range ah cells are from those children's ride on toys.

powerwheels, jeeps and the likes run on 12v low ah packs

[Wailin]

I think my skywatcher 7ah power tank is having issues as it seems to be taking longer to charge it and at the moment its still charging with the RED charging light on but also the GREEN fully charged light seem to be coming on and even though its not bright green now it seem to be getting brighter.

Matt I'm having the very same issue as you with the 7Ah power tank. Mine is brand new and I charged it for over 30hrs and the red charging light was still on. I didn't want to overcharge so I stopped. I also have a 17Ah which doesn't have this problem and the green light comes on when fully charged. Wonder should I leave the 7Ah charge longer until the charging light goes off.

[GyCx]

Fully charged thanks James

[Mad Dog]

Nice thread, Unfortunately after a long break from astronomy due to other commitments I find that my battery has also died. When I try to charge it , it just makes a clicking sound and the charge lights go out and nothing. Is there a chance this is salvageable? Thanks guys.

[m37]

I know this is not exactly a current thread (pun intended) but I bought a Maplin 5 in 1 today and spoke to the bloke in the shop about battery life.

Basically, he said the instructions should be followed to the letter (carry out initial 38 hour charge and never let it fall near the red, always charge between uses) and it should be fine.

If it's being stored it needs to be charged every 2 months, and I believe the light stays red and doesn't go green; it's just a mains light. You have to just charge it for the stated length of time then stop charging. Not ideal but I will be posting back about performance over an extended period.

This probably isn't much use to anyone with an already dead battery but I thought it might be of use to someone.

cheers

[Geordie mc]

I have the Maplins 3:1 jump start thingy. Is it difficult to take apart and just add the extra cigar adapters to get muliple outputs? I'd like to add a dew heater and maybe a ccd camera.

[bodtwo]

Good tip, especially looking out at the frost this morning.

[osbourne one-nil]

I'm guessing my 12v 7ah/20ah battery is dead. I read this, thought "oh dear", have tried charging it, but nothing. Luckily it was only £20, but still....lesson learned. 

[osbourne one-nil]

^{Ended up replacing my previous leisure battery with a Powertank from FLO. It says on the sticker to charge for 24 hrs before first use, which seems clear cut, but then I read that you want to stop charging once the fully charged light comes on. Mine had the fully charged light on straight away, so which advice should I take?!}

Edited January 20, 2014 by osbourne one-nil

[alan potts]

James,

Every word true, I have rescued mine but I don't know if it will survive for long.

[Physopto]

Hi All,

 Lead acid batteries are really a pain in the rear. What ever the stated capacity please take with a pinch of salt! It depends upon age,  temperature, type of lead acid makeup and various other things. Most lead acid batteries really can only supply about half to three quarters of their stated capacity at the sorts of currents we tend to ask of them.  A 100 Ah battery should on paper give 100 hours at  a 1amp discharge rate. At 10 amps discharge you may expect 10 hours. Not true! The higher the discharge rate the less you will get out of them. Lead acid batteries give a constantly reducing voltage slow curve discharge. Think of a hose held horizontally discharging water, the water leaving the hose curves downwards until it hits the ground. That is what you will see as the voltage reduces at a constant current discharge. The higher the current the quicker the fall off of voltage. As astronomers we want the battery to give nominal 12 volts. A fully charged lead acid battery shows 12.8 volts approximately (dependant upon battery type). At half charge it will show 12.4 volts. But fully discharged it will show around 10.6 volts. In other words not a linear discharge voltage fall.

Personally I try to keep my batteries on constant charge whilst in use. I charge them up, then they are kept on a maintenance charge of 13.6 volts. Trouble is that CCD cameras often state that the voltage needed is to be around 12.6 volts but not above. Whereas mounts such as the NEQ6 require above 12 volts to be stable but not above 14 volts (I believe). Instructions for QSI CCD camera state that you should only use the power block to supply power. I don't like 240 volts in the field, not safe! The camera alarms when below 11 volts, minimum rated voltage  or above 14 volts the maximum rated operating voltage. Either case can cause a failure in the electronics. Remember in the field it would be easy to drop below the 11 volt range in the cold, (batteries hate cold and their output drops significantly).

My answer is to us a DC to Dc convertor. Any input from the battery from 10 to 15 volts will give an output about 12.6 volts at up to 5 amps (60 watts). These are available from several sources on the internet. They were initially made for the caravan/motorhome market I think, as above 12.6 volts can damage so called 12 volt  TVs. There is plenty of info on the web. They are available from about £13/14 up to £40, dependant upon maker. These devices are about 75 to 80% efficient.

Lastly lead acid batteries hate to be discharged. Even worse they may fail if left in a discharged state for even a short period of time. Each time they are partially discharged they lose capacity.

Leisure batteries are the best at recovering from partial discharge, car batteries need to be fully charged at all times, they are only designed to give large currents to start the engine then be recharged immediately when the engine runs the alternator.

If you look at the makers statistics for any battery it should give the required info. From a brand new 100 Ah leisure battery I do not expect to get more than 30 to 35 Ah before the battery falls below 12.4 volts if it is not being charged in any way! After that it will fall below 11.5 volts very quickly and we all know how that feels when we hear the anguished cries *!@%$*  dead battery etc.,

I hope this may help anyone reading.

Derek

Regards,

 Derek

[griz11]

I use a jump starter battery on my rig too. You can catch them on sale frequently. I think I paid 21 bucks for mine. Lasts all night even with the dew heater on. Get one with a cig adapter on it and a 4 way tap with usb ports and you will be able to power most anything you need. I think I paid 7 bucks for one of those. Problem with the jump starters is the weight costs more to ship them than to buy sometimes so try and find them locally.

Griz

[Ajohn]

Gunson have made an automatic batter charger with a float setting for permanent connection for a long long time. It works rather well.

John

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[Geoff Lister]

I have had one of these car starter/air compressor packs for many years. I leave it plugged in to a timer socket, and it gets topped-up for about 30 minutes a day. If I am not expecting to use my car for a period, I leave the pack connected across the car battery and that ensures that the car battery is also kept healthy. The charging regulator circuit in the pack turns off the charge current (about 0.5A) when the top-up is adequate. I get a reliable start even if the car has not been used for over a month.

Geoff

[garryblueboy]

Mine died on Sunday dead as a dodo went and brought a good Tracer  lipo so only need to charge every six months if not used plus so much smaller and lighter than my old 17amp power tank 

[Bagnaj97]

Lidl have got their battery chargers in from tomorrow - https://www.lidl.co.uk/en/Non-Food-Offers.htm?articleId=6216

Hopefully it'll be of use to somebody for charging powertanks/jumpstarters/leisure batteries.

[TSRobot]

I use a 1.5 watt trickle solar panel from Maplins to top up my power tank. It lived in my shed for several years and still seems ok. I'm no expert though. I do charge it from the mains every now a then. It's 10 yrs old now.

[Limerick John]

On 28/07/2009 at 17:48, James said:

At this time of year where many of us don't get out to do any viewing for a few weeks it's worth remembering to charge up your PowerTanks/batteries every 3-4 weeks as, in common with all lead acid batteries, your PowerTank's charge needs to be kept topped up to avoid damage. I thought I'd post this reminder to avoid any disappointment when the longer dark nights come round again...

Lead acid batteries lose charge even when not being used and allowing the battery to discharge power over several periods of use without recharging can lead to the situation where the battery cannot be charged with the supplied charger.

If the battery discharges too far this can permanently damage it, or at the very least considerably shorten its lifespan. To avoid this the battery must be charged before, and regularly during, periods of storage and after every use.

If your battery has drained completely or hasn't been charged after each period of use there is a chance it can be rescued by the use of a deep charger otherwise you may find it impossible to recharge at all - not something you want to find out as the longer nights come round again.

James

Great advice. I replaced the batteries on my two Halford powerpacks last year after ten years of use following the advice above. They were still usable but drained quickly. I picked up two new 20 AmpHr batteries locally and put them into the units. Good as new!

[BGazing]

Celestron powertanks are the bees knees. Pricey but yet to fail in freezing conditions and have useful LED lights too. Going on and on and LiFePo avoids some of the lead pitfalls...

[jefrs]

A Power Tank battery that seems on its way out may be recharged with a Noco Genius G3500 which is a small intelligent charger for motorcycles. It is a 3.5A charger but has a 1A setting for small batteries as used on motorcycles, and in the Power Tank. To charge the Power Tank connect to the red and black screw terminals with the Power Tank set to OFF.  The G3500 will indicate when the battery is fully charged.

Small lead acid should not be charged at more than 1A rate. Use the 1A AGM battery setting. Do not use any 3.5A setting. The G3500 is far more 'intelligent' than an optimiser. It also has a recovery mode that may bring a lead acid back from dead.  Please note I use the word 'may' here and above, if the battery is completely dead it will not work; I have recovered a deeply discharged but fairly new motorbike battery that has continued to work perfectly.  A charged lead acid 'in storage' should last up to six months without any current drain; I have a reminder set up for every two months to check all lead acid and lithium batteries, and recharge as required.  Lead acid batteries do not like being on continuous charge (small current), nor being recharged too often; but they do like being fully charged (full current) when they are recharged; leave them on an intelligent charger for 24h.

If the Power Tank battery is dead it will not recharge.  It is a fairly standard burglar alarm type leisure battery, replacements can be obtained from the usual suspects online.

Perhaps keep the Power Tank in the car plugged into a lighter socket so that it charges whenever the car is running, as the car's own battery does. Not into an always-on socket that may drain the car's battery.

[jfrijhoff]

I had no idea, good to know!!