Tracer LiFePO4 Batteries

[FLO]

We have today increased our range of compact Tracer LiFePO4 power packs to include 3.5, 7, 12, 16 & 24 Ah models with the same shape/style as the earlier Tracer Lithium Polymer batteries. 

LiFePO4 batteries are the safest battery technology available and feature significantly higher charging life-cycles than even the Tracer Lithium Polymer battery packs.

For comparison: 

Tracer 12v 24Ah LiFePO4

Tracer 12v 22Ah Lithium Polymer

 

[psamathe]

I have one and an impressed with it.

I understand it has a flatter voltage curve than the Lithium Polymer (i.e. maintains voltage better as the battrey discharges).

One thing I have found is that the built-in power meter can read a bit low when in use.  I am told this is because the battery voltage curve is very flat (i.e. maintain voltage as the battery discharges), the power gauge needs to be very sensitive (i.e. very little voltage difference between full and empty) and thus is more sensitive to loads causing lower reading.  e.g. Full battery after a couple of hours driving scope, two dew heaters, spinning disk laptop (screen on) shows a couple of bars down from full.  But pack-up put everything away and then test gauge and it's recovering.  Not a problem (just surprised me 1st use before I appreciated the reason).

Ian

[Physopto]

They are a great battery for consistent/average low discharge rates and will last for a longish session.

But..................

The problem with these batteries is if you need a larger than low discharge rate,  is how do you charge them. You cannot alter the charger to charge at the same time as they are in use, because it negates the guarantee. You also will need a larger than 1.65 Ah charging rate if using at a large discharge rate, I believe there is a bigger rate charger available.

Tracer also have another range with two connections available. These can be charged at the same time a being discharged and are housed in a Pelicase. I stipulated that some time ago on my order with them through the Widescreen Centre. After they altered their range to accommodate my wishes the prices went up by £200 to new customers; for one extra socket and two connecting wires!

That being said they are very good batteries.

Derek

[Joe12345]

Slightly off topic, but...... I was thinking of getting a power pack, which would power 0.25 amps of dew heaters, and sometimes this (sw supatrak 130p). Any idea what ampage that would give in total? I'm trying to decide whether to get one of these with a little less ampage, or the other version with a slightly shorter lifetime. Thanks

[psamathe]

3 minutes ago, Joe12345 said:

Slightly off topic, but...... I was thinking of getting a power pack, which would power 0.25 amps of dew heaters, and sometimes this (sw supatrak 130p). Any idea what ampage that would give in total? I'm trying to decide whether to get one of these with a little less ampage, or the other version with a slightly shorter lifetime. Thanks

I believe the LiFePO4 range can provide a continuos 10A output.  Unsure where you get the "a little less ampage" from.  I think if you are looking at taking more than 10 amps ...

[Physopto]

Better to have more Amp Hours than you need than too little. Costly to have to buy a new one because of added gear later on.

[psamathe]

1 hour ago, Physopto said:

They are a great battery for consistent/average low discharge rates and will last for a longish session.

But..................

The problem with these batteries is if you need a larger than low discharge rate,  is how do you charge them. You cannot alter the charger to charge at the same time as they are in use, because it negates the guarantee. You also will need a larger than 1.65 Ah charging rate if using at a large discharge rate, I believe there is a bigger rate charger available.

Tracer also have another range with two connections available. These can be charged at the same time a being discharged and are housed in a Pelicase. I stipulated that some time ago on my order with them through the Widescreen Centre. After they altered their range to accommodate my wishes the prices went up by £200 to new customers; for one extra socket and two connecting wires!

That being said they are very good batteries.

Derek

These LiFePO4 packs (the ones in the grey cases) have separate output and changer connections.  The output if via the T-bar connector and the charger plugs into a 2.1/5.5 socket up by the battery gauge.  Don't quote me and don't act on this but I believe the two connections are just wired in parallel.

I believe you can get faster chargers (up to 4 amps).  My worry about using and charging at the same time is you would in effect be putting a higher (charging) voltage into all your gear and in effect driving your gear from the charger.  I also have a mains>12V DC pack so if I have mains available I use that instead of the battery.

If you have mains available but still want to use batteries, then I'm sure there must be some neat switching way to switch between battery packs without breaking (i.e. battery 1 in use, add battery 2 so running batteries 1&2, then switch out battery 1 leaving everything running on battery 2 alone - then start charging battery 1).   ***** See post below which highlights the dangers of this idea, particularly with this battery technology *****

Ian

[Physopto]

If they have separate input and output that is great. The Pelicase type did not have that a year or so ago.

Yes, it can be a problem in charging at the same time as using for the equipment. I had problems with my lead acid type batteries due to the charger going up to 14.4 volts. This caused alarms and failure of the QSI camera I had (maximum  is 14 volts then alarms), necessitating shut down and reboot of computer software and camera.

To get around this you can use DC/DC convertors that were originally meant for the caravan/motorhomes. They output 12.2 to 12.4 volts at all times and can handle 60-70 watts, these are usually about 85-90% efficient. Their supply voltage can be  anything between 10 to 16 volts. There are more expensive solutions, but mostly these will protect equipment easily. They were meant to protect 12 volt TVs from the higher voltages supplied by alternators. Most 12 volt TVs cannot take more than 12.6 volts with out damage to their electronics.

It all depends upon how much you need or want to supply from the DC source and for how long.

Trying to connect in another fresh battery can cause big problems especially as to LiFePo4 type or LiPo4 batteries. They can dump very large currents into the circuitry of the depleted battery and this can be very dangerous. The internal resistance of these batteries is very low. Then the disconnection will cause a spark because of the large current flowing.

Derek

[psamathe]

2 minutes ago, Physopto said:

If they have separate input and output that is great. The Pelicase type did not have that a year or so ago.

...

Talking about the 2 tone grey LiFePO4 packs (not the dark ones with yellow tops that look more car battery like), then mine certainly has physically separate output and charging sockets (though as I said I do not believe them to electrically separate so plug in your charger and you will probably be connecting your charger straight onto all your gear.

I do not know enough about charging currents and voltages to comment on the technicalities.  I went for the most powerful 12V LiFePO4 pack thinking that due to their longevity (last many years) you don't get the chance to upgrade.

Slightly related question: If your chosen pack is not lasting long enough, can you buy a 2nd and use one to power e.g. mount and dew heaters and 2nd pack to power laptop and cameras (basically split the consumption across the two packs so the draw ends-up discharging them at the same time).  Would this cause problems with floating negative voltages (as the 0v would not be common so you might be doing something I remember along the lines of "earth loops", thinking as with a metal mount/scope if the 0v is connected to the mount, to the scope and thus connected through to the camera which is connected to the 0v of a different battery).  Or are there ways/precautions that allow this ? (this is where I am technically out of my depth).

n.b. Having said above about the 4A charger being available, I think that the 4A charger is the one that comes with the battery (i.e. not a more powerful optional extra).

Ian

[Physopto]

Lithium batteries have to be balanced. They have special balancing circuitry inside the battery packs. Each cell is balanced against the others as their characteristics vary. I would not  advise connecting two in parallel unless the manufacturer says it is safe to do so.

I use two 40Ah  LiFePo batteries. One actually manufactured completely by Tracer Cost £650. The price then went up to £850. So I bought a second bare Tracer battery and also a Pelicase off the web. I fitted it into the Pelicase and wired it up with identical plugs and sockets. Cost just under £600. To all intense and purposes they are identical.

BUT  the batteries are completely separate.

I do not use them to power the same gear. One powers the CCD and ancillary gear. The other powers the mount electronics and Dew heaters. I use two separate 10 Amp Hour chargers made by Tracer, one for each battery.

Even though I was an engineer experienced in electrical installations, I also checked with Tracer before I bought the first battery that they could be charged safely whilst being used. A manufacturers recommendation for their equipment is of paramount importance.

Derek

[Joe12345]

1 hour ago, psamathe said:

I believe the LiFePO4 range can provide a continuos 10A output.  Unsure where you get the "a little less ampage" from.  I think if you are looking at taking more than 10 amps ...

Sorry if I was unclear.

Each different powerpack has a different rating in Ah. From what I understand, the higher this is, the longer it will power my equipment. If I have a 0.25A dew heater and an 8Ah battery, I should be able to power it for 32hrs, right? So if I want to power my mount as well as the heater, it will last less time. So what I'm really asking is how many amps will my mount draw?

[psamathe]

50 minutes ago, Physopto said:

Lithium batteries have to be balanced. They have special balancing circuitry inside the battery packs. Each cell is balanced against the others as their characteristics vary. I would not  advise connecting two in parallel unless the manufacturer says it is safe to do so.

I use two 40Ah  LiFePo batteries. One actually manufactured completely by Tracer Cost £650. The price then went up to £850. So I bought a second bare Tracer battery and also a Pelicase off the web. I fitted it into the Pelicase and wired it up with identical plugs and sockets. Cost just under £600. To all intense and purposes they are identical.

BUT  the batteries are completely separate.

I do not use them to power the same gear. One powers the CCD and ancillary gear. The other powers the mount electronics and Dew heaters. I use two separate 10 Amp Hour chargers made by Tracer, one for each battery.

Even though I was an engineer experienced in electrical installations, I also checked with Tracer before I bought the first battery that they could be charged safely whilst being used. A manufacturers recommendation for their equipment is of paramount importance.

Derek

I was not thinking about paralleling them but rather separate gear but just wondering if the fact that the 0v on each battery would probably end-up being connected through the metal gear - wondering if that could cause a problem.

Ian

[Physopto]

Ian,

As far as I know the negative is not connected to earth (the casings or cases). In reality earth should be connected to the actual ground, not important in low voltage DC for our purposes unless there is a short. The negative and positive are completely separate.

In an automobile the body of early vehicles were connected to positive,  this was changed later on, causing quite a few problems, to the negative side. The car or vehicle body was one of the conductors.

In most electronics I have come across this is not so. Casings are connected to the  house earth for safety so no connection  should be made to earth from either positive or negative.

(Another point often overlooked is that electrons flow from negative to positive in DC circuits. Electrons are the charge carriers. The only change to this is in "P" type doped diodes and transistors where the holes are regarded as the charge carriers.)

Last point there is no 0 volt on a battery. It is either positive or negative at what ever voltage the battery is. i.e. +12 volt or -12 volt. In electronics it is common to refer to 0 volt line, but this is a relative assumption to other circuits.

Hope this helps a bit. I am not an electronics expert just an hobbyist.

Derek

 

[Physopto]

1 hour ago, Joe12345 said:

Sorry if I was unclear.

Each different powerpack has a different rating in Ah. From what I understand, the higher this is, the longer it will power my equipment. If I have a 0.25A dew heater and an 8Ah battery, I should be able to power it for 32hrs, right? So if I want to power my mount as well as the heater, it will last less time. So what I'm really asking is how many amps will my mount draw?

Probably me missing the point sorry. What you say is sort of correct. In ideal conditions absolutely right. But due to battery characteristics you would get a wee bit less. The Li type batteries are very good in that respect, you would get almost what you say. I just don't know what the draw of your mount would be. Highest will be on slewing. The initial movement usually takes the most current in overcoming inertia and friction. The actual slew the next. On tracking very little in respect to slewing. You will have to check  with the manufacturers information. If you change targets often you will use more battery power. if not then less.

li batteries will give you almost full discharge of rated power capacity, whilst lead acid about 1/2 to 3/4 if lucky before the supply voltage drops considerably.

Derek

[Joe12345]

Thanks

I didn't really consider that it would use more power when you slew it more. It's either 3.5Ah or 7Ah, and I would probably use it for 6hrs absolute max.

[Physopto]

34 minutes ago, Joe12345 said:

Thanks

I didn't really consider that it would use more power when you slew it more. It's either 3.5Ah or 7Ah, and I would probably use it for 6hrs absolute max.

You will need also to consider the current draw for ancillary equipment. So dew heaters, how many, what size? The ambient temperature will affect the current drawn if using a dew heater controller, as lower temps mean more power used. If you do not use a controller you will need to account for the full draw all the time dependant upon dew heater size. That method will also mostly waste power and probably overheat the area concerned. 

Usually for most mounts a figure of 0.5 to 1 amp may be drawn during tracking and up to several on a slew, say 4 amps. Slews only last for a few seconds really. So if you count on an average of around 1 amp all the time you should be safe. Discounting the dew heater for the moment, a 20 AH Li ion type battery should last easily all night. The same cannot be said for a lead acid of the same rating. Temperature will affect the capacity of the lead acid types considerably.

hope this helps you.

 Derek

[psamathe]

34 minutes ago, Physopto said:

You will need also to consider the current draw for ancillary equipment. So dew heaters, how many, what size? The ambient temperature will affect the current drawn if using a dew heater controller, as lower temps mean more power used. If you do not use a controller you will need to account for the full draw all the time dependant upon dew heater size. That method will also mostly waste power and probably overheat the area concerned. 

Usually for most mounts a figure of 0.5 to 1 amp may be drawn during tracking and up to several on a slew, say 4 amps. Slews only last for a few seconds really. So if you count on an average of around 1 amp all the time you should be safe. Discounting the dew heater for the moment, a 20 AH Li ion type battery should last easily all night. The same cannot be said for a lead acid of the same rating. Temperature will affect the capacity of the lead acid types considerably.

hope this helps you.

 Derek

You should be able to find max current taken by your dew heaters (e.g. http://www.thousandoaksoptical.com/dew.html).  If you have a controller you could start estimating what %age max current or just base your calculations on the max.

I went for max battery capacity as they (LiFePO4) last a long time and I am bound to end-up getting more gear (cameras, auto-guiding, etc.) over the life of the battery.  Better to have a battery with some capacity left at the end of an observing session than one that runs out just when you are getting on well.  But that needs balancing against the cost of the battery (and they are not cheap).

Ian

[Joe12345]

My dew heaters are homemade, the eyepiece one with 7*15ohm resisters, and the telrad one with 3*27ohm ones. So each would give out 1.5 watts, so 3 all together. Divide that by 12v and that says that 0.25A will be spent on dew heating. Then if the mount uses 1A, that would be 1.25A. If the temperature uses up power, say double in the worst case, then it would be using up effectively 2.5A? In that case, a 3.5Ah battery would last 1.4hrs, a 7Ah 2.8hrs, a 12Ah 4.8hrs, a 16Ah 6.4hrs etc. I'm not an imager and don't plan to be one for at least 10yrs, so there isn't really a risk of needing to power more things, so I think it will either be the 7Ah or 12Ah. Thanks for all your help

[Physopto]

7 hours ago, Joe12345 said:

My dew heaters are homemade, the eyepiece one with 7*15ohm resisters, and the telrad one with 3*27ohm ones. So each would give out 1.5 watts, so 3 all together. Divide that by 12v and that says that 0.25A will be spent on dew heating. Then if the mount uses 1A, that would be 1.25A. If the temperature uses up power, say double in the worst case, then it would be using up effectively 2.5A? In that case, a 3.5Ah battery would last 1.4hrs, a 7Ah 2.8hrs, a 12Ah 4.8hrs, a 16Ah 6.4hrs etc. I'm not an imager and don't plan to be one for at least 10yrs, so there isn't really a risk of needing to power more things, so I think it will either be the 7Ah or 12Ah. Thanks for all your help

Sorry if this seems  a daft question but are the resistors in series or parallel. Also are they (each dew heater) connected to the same battery supply in parallel?

If the resistors are connected in parallel over 12 volt supply then the resistance is 1/r1 +1/r2 +1/r3 ......1/r7 = 1/R(total)

If in series it is simply r1 +r2.....+r7 = R(total)

Basically asking how you have them connected?

 

Derek

[Joe12345]

In series. But the separate heaters will be parallel. I followed this guide

[psamathe]

9 hours ago, Joe12345 said:

My dew heaters are homemade, the eyepiece one with 7*15ohm resisters, and the telrad one with 3*27ohm ones. So each would give out 1.5 watts, so 3 all together. Divide that by 12v and that says that 0.25A will be spent on dew heating. Then if the mount uses 1A, that would be 1.25A. If the temperature uses up power, say double in the worst case, then it would be using up effectively 2.5A? In that case, a 3.5Ah battery would last 1.4hrs, a 7Ah 2.8hrs, a 12Ah 4.8hrs, a 16Ah 6.4hrs etc. I'm not an imager and don't plan to be one for at least 10yrs, so there isn't really a risk of needing to power more things, so I think it will either be the 7Ah or 12Ah. Thanks for all your help

I think "future" (i.e. not imaging) would depend on what battery technology you decide.  The life of the LiFePO4 means that you have to think a low way ahead.  Even without imaging, what about laptop driving scope ?  Other things people plug-in ?

Ian

[Physopto]

20 minutes ago, Joe12345 said:

In series. But the separate heaters will be parallel. I followed this guide

OK thanks. For the eyepiece not sure if that will be enough, but easily altered if need be. As a round figure that's I²R = power in watts. 0.1143² *105 = 1.37 watts !!

Have you actually tried this to see if it keeps dew at bay? If not I would check it out. Easy to do just leave it out with the dew heater going and check to see if it dews up at all over several hours. It does not need to be on a telescope.

The Telrad should  be OK. 12 volts over 81 ohms is about 0.15 amps. So around 0.15² * 81 = 1.8 watts. I use a 220 Ohm 5W resistor, ( at 12 volts that's 0.65 watts) but it is controlled by a pulse width modulated (PCM) supply. In other words my actual average wattage is less for the Telrad. It works fine in even the heaviest dewed nights.

 

If you ever decide to make another dew heater band I suggest using the ladder network method. If one resistor goes faulty (open circuit) the rest are still in operation. Whereas in a series connected make up if one goes faulty (open circuit) the system  goes dead as there is not continuity. if on the other hand a resistor goes short circuit the load is increased  and the system gets much hotter (less resistance), due to the current in the circuit increasing.

Good luck with your endeavours.

Derek

[Joe12345]

Thanks very much for all your help!

I've taken out 2 of the resistors on the Ep heater, so it should be a bit hotter now.

I'll test it at the weekend, so hopefully there'll be a high dew point.

[Physopto]

Last question are you using any form of heating control? If not it is very cheap to do and easy.

See here. http://www.banggood.com/Wholesale-LED-Light-Dimmer-Brightness-Adjustable-Control-Controller-12V-8A-p-27703.html

[Joe12345]

Two of them are on their way from China - I think they're at the post office, but that may be something else. Thanks again, Joe