DIY powertank - Electrical Diagram

[Vox45]

So I bought all the parts I need to make my 1st powertank. Before I start a fire or blow up something I would lilke your comments on this diagram (crude)

- 2x 12v 7.5Ah lead-acid batteries in parallel to get 12v 15Ah

- I thought of isolating each battery with a 7.5A fuse and then link them in parallel and have a 15A fuse for the both of them (overkill maybe)

- not sure were to put the voltmeter, I assume it as to in parallel too

- the usb component I got are in a 12V cigaret lighter plug, so I assume that they are also fuse protected

I am not an electrician so all comments and critics are welcome

[Vox45]

Noone ? Did I get it right on my 1st try ?

It is really the voltmeter that I cannot figure.

[knobby]

The picture is very small but the volt Meter just needs to be connected to the + and - of battery ... Possibly worth putting a push switch in between battery and voltmeter just in case it drains the battery when idle

[michael.h.f.wilkinson]

I am not sure 15Ah is going to be adequate, and do make sure they are deep-cycle batteries, or else they will not last long. My 17Ah was drained too far so it got damaged, and replacement by a 22Ah proved very useful. I only really ran an RA motor from it, rarely a dew strip and still managed to drain it too far (storage in a cold garage didn't help either). Using a bigger battery allows you to cycle it less deeply, and allows more stuff to run from it.

[Vox45]

You can click on it and it will get bigger (that's what she said)

I do have an on/off switch between the voltmeter and the +/-  so that would serve the same function as the push switch correct ?

[Vox45]

I am not sure 15Ah is going to be adequate, and do make sure they are deep-cycle batteries, or else they will not last long. My 17Ah was drained too far so it got damaged, and replacement by a 22Ah proved very useful. I only really ran an RA motor from it, rarely a dew strip and still managed to drain it too far (storage in a cold garage didn't help either). Using a bigger battery allows you to cycle it less deeply, and allows more stuff to run from it.

I use deep cycle (UPS) batteries and eventually will replace those by more Ah (thinking of 60Ah) I just had 2x 7.5Ah availlable so that will be enough for now.

Thinking about it, I realize that the wiring needs to support 60A for my future setup (changing the fuse is easy, but redoing the wiring is a pain) ... Is this an issue if I run lower Amp batteries on higher Amp wire or it does make any difference which type of wire as long as it supports the maximum Amp without melting ?

[michael.h.f.wilkinson]

Just go for thick wires, they will happily carry less current.

[Lonestar70]

I use deep cycle (UPS) batteries and eventually will replace those by more Ah (thinking of 60Ah) I just had 2x 7.5Ah availlable so that will be enough for now.

Thinking about it, I realize that the wiring needs to support 60A for my future setup (changing the fuse is easy, but redoing the wiring is a pain) ... Is this an issue if I run lower Amp batteries on higher Amp wire or it does make any difference which type of wire as long as it supports the maximum Amp without melting ?

Hi,

The size of the battery does not dictate the size requirement (gauge) of the wiring... the TOTAL load current does.

As shown in your diagram, the maximum Total Load would be 7.5amp (dictated by the 7.5amp fuses in each battery lead).

The 15Amp fuse, in this case is actually redundant.

The first thing to do is calculate the Total load current required.

To do this you need to establish the max current drawn from each individual outlet and add them all together... then fit a fuse just slightly higher than this... The15Amp may be about right for this.

The 2 x7.5Amp fuses serve no real purpose and may actually give you problems when charging the batteries ...so remove them.

The wiring need only be large enough for this load current, but larger wire will do no harm, and may serve you for any later additions... in your case I would recommend 1.5mm² or 2mm² cross section cable.

If you are not using individually fused cables on all your outlets, then I would suggest that you fit an individual fuse in each output connection... rated for the load expected.

E.G. a 5Amp fuse for the mount outlet and say a 3Amp for a dew heater outlet and the spare 12v outlet... the USB socket would be 1Amp (500mA per usb)

Your Voltmeter should be fine as shown on your diagram (i.e. between switched + and common -).

The other problem is charging... Unless your batteries are properly matched then one will dominate and will discharge faster than the other... the slower battery will then try and charge the faster one.

This imbalance will also be a problem if you charge the batteries connected in parallel... one will hog the input current and could well blow the series 7.5Amp fuse...the other battery will not get enough charge current.

Even using an intelligent charger would not resolve this... the charger would be influenced by the dominant battery.

It is generally not good practice to charge deep cycle batteries in parallel... particularly when they fall below their 'Absorption Charge' level (approx 70% of fully charged level).

I hope this is of some help.

Best regards.

Sandy.

[Physopto]

I use deep cycle (UPS) batteries and eventually will replace those by more Ah (thinking of 60Ah) I just had 2x 7.5Ah availlable so that will be enough for now.

Thinking about it, I realize that the wiring needs to support 60A for my future setup (changing the fuse is easy, but redoing the wiring is a pain) ... Is this an issue if I run lower Amp batteries on higher Amp wire or it does make any difference which type of wire as long as it supports the maximum Amp without melting ?

Hi Michael,

 Use the biggest wire CSA  you can. Put fuses in line with each battery. If you do parallel up two batteries you should really use a power diode in each +ve line. This will protect the batteries from each other in case of a fault. By this I mean that a battery as it gets older will possibly fail (internal short) and then discharge the other battery.

 The diodes will reduce the output voltage by about 0.5 volts as seen by the equipment. (pn junction forward voltage drop).

BUT.

It would be better to only use one battery of a larger size.

In my circuits I use 2,5 mm CSA wire or 4mm if possible. As the current increases the voltage will drop due to the wiring resistance. Bigger wire less resistance at the same current. Wire CSA depends upon what you are trying to power.2.5 mm wire can take 90 amps OK at 12 volts. So in theory a 90 amp fuse, but not really practical as the wire would still get hot. Current rating also depends upon the environment, by that I mean if the wires are in the open air (air circulation to remove excess heat), or enclosed where heat can build up.  See this for a simple calculation http://www.the12voltshop.co.uk/Shop/about-cable-sizes.html

Fuse rating should depend upon the maximum rated current for each device (minus a bit for safety). Each output should be correctly and  individually fused for its intended purpose. The battery should also be fused for the maximum you intend to output from it, but obviously below its maximum safe level. Lead acid batteries can only output power at certain rates for certain periods of time. A 100ah battery could say output 10 amps for about 4 hours, before it seems to be exhausted. It may output 1 ah for 70 hours. It depends upon the type of battery, i.e deep cycle or starter.

You will only usually get about 50 to 75% out of a lead acid battery before the voltage goes too low for our uses. So picking the correct size for the intended purpose is important.

Hope this helps,

 Derek

[Vox45]

The other problem is charging... Unless your batteries are properly matched then one will dominate and will discharge faster than the other... the slower battery will then try and charge the faster one.

This imbalance will also be a problem if you charge the batteries connected in parallel... one will hog the input current and could well blow the series 7.5Amp fuse...the other battery will not get enough charge current.

Even using an intelligent charger would not resolve this... the charger would be influenced by the dominant battery.

It is generally not good practice to charge deep cycle batteries in parallel... particularly when they fall below their 'Float Charge' level (approx 60% of fully charged level).

I hope this is of some help.

Best regards.

Sandy.

This helps a lot thanks !

Regarding the charging of the batteries, I was thinking of unplugging the batteries and charge them indivually. I did not thinks of the fact that one would try to recharge the other while I was using the rig

I think that using only one bigger battery would be less of a hassle....

[Vox45]

Hi Michael,

 Use the biggest wire CSA  you can. Put fuses in line with each battery. If you do parallel up two batteries you should really use a power diode in each +ve line. This will protect the batteries from each other in case of a fault. By this I mean that a battery as it gets older will possibly fail (internal short) and then discharge the other battery.

 The diodes will reduce the output voltage by about 0.5 volts as seen by the equipment. (pn junction forward voltage drop).

BUT.

It would be better to only use one battery of a larger size.

In my circuits I use 2,5 mm CSA wire or 4mm if possible. As the current increases the voltage will drop due to the wiring resistance. Bigger wire less resistance at the same current. Wire CSA depends upon what you are trying to power.2.5 mm wire can take 90 amps OK at 12 volts. So in theory a 90 amp fuse, but not really practical as the wire would still get hot. Current rating also depends upon the environment, by that I mean if the wires are in the open air (air circulation to remove excess heat), or enclosed where heat can build up.  See this for a simple calculation http://www.the12voltshop.co.uk/Shop/about-cable-sizes.html

Fuse rating should depend upon the maximum rated current for each device (minus a bit for safety). Each output should be correctly and  individually fused for its intended purpose. The battery should also be fused for the maximum you intend to output from it, but obviously below its maximum safe level. Lead acid batteries can only output power at certain rates for certain periods of time. A 100ah battery could say output 10 amps for about 4 hours, before it seems to be exhausted. It may output 1 ah for 70 hours. It depends upon the type of battery, i.e deep cycle or starter.

You will only usually get about 50 to 75% out of a lead acid battery before the voltage goes too low for our uses. So picking the correct size for the intended purpose is important.

Hope this helps,

 Derek

I knew it ! There is more to it than my simple crude diagram...

I will study all these answers and come back with a different diagram.

Thanks for your valuable input Physopto

[Physopto]

Hi Michael,

Just remember you have to lift it! Ouch my back!!

A 110 ah battery weighs about 22 to 26Kg. There are ne4w types available using Calcium. Mine weigh less than the older lead acid types. For some more info on battery voltages etc., see POST 63 in (A reminder about charging your PowerTanks).

Derek

[Vox45]

Hi Michael,

Just remember you have to lift it! Ouch my back!!

A 110 ah battery weighs about 22 to 26Kg. There are ne4w types available using Calcium. Mine weigh less than the older lead acid types. For some more info on battery voltages etc., see POST 63 in (A reminder about charging your PowerTanks).

Derek

Yes weight is always an issue

[Vox45]

So after carefull consideration I decided to go the PowerPanel route instead of the powerbox route

- Easier to carry around

- can plug to any battery I come across, even a car battery if reeeaallly needed

- can be velcroed at the mount with only one lead cable to the battery

- not tied to a particular battery size that HAS to fit the box ... battery sits outside

I will only need to figure out how to make an external cable from the battery to the panel. I was thinking of using XLR on one end and spade/crocodile on the other end.

- spade for smaller batteries

- crocodile for larger ones

Therefore the cables would have to be 15A for the spade cable and 25A for the crocodile I would guess...

I'll try to come up with an updated diagram

[Vox45]

So after rethinking my needs, I made a second design.

Note that I will only use one external battery (see post above) as I will build a powerpanel instead of a powerbox.

I will use an XLR or speakon connector (not decided yet) to connect to an external battery.

I wonder if I need to put a voltage regulator somewhere in that design ? I would think I need that to protect the devices plugged in... Any thoughts on that ?

(click to enlarge)

The XLR connector is probably not properly connected in this diagram, did not know which way it goes ...

[Alien 13]

I did something similar with mine, DC-DC convertors are a good idea if you want to power multiple I tems (usb, camera, 6v mount) I can either use mine with a 12v battery or a 6A mains adaptor in the house and fed outside.

Alan

[Physopto]

So after rethinking my needs, I made a second design.

Note that I will only use one external battery (see post above) as I will build a powerpanel instead of a powerbox.

I will use an XLR or speakon connector (not decided yet) to connect to an external battery.

I wonder if I need to put a voltage regulator somewhere in that design ? I would think I need that to protect the devices plugged in... Any thoughts on that ?

(click to enlarge)

The XLR connector is probably not properly connected in this diagram, did not know which way it goes ...

To protect your devices you could use the DC/DC convertors. But you will need enough power capability to power each device possibly at different voltages. Sounds odd but manufacturers all claim 12 volt. But if you read their blurb some say 12 volt others state that their devices work from 11 volts up to 14 volts (as in EQ8). QSI state that their cameras work between 12 volts and 14 volts but alarm, (actually mine shuts down) if above 14 volts. Have a read of this thread,

http://stargazerslounge.com/topic/46532-a-reminder-about-charging-your-powertanks/

second to last post in particular. I tried to explain it  there.

Small DC/DC convertors just have not got the power capabilities. Don't forget that the more power your devices take the bigger the voltage drop in the line from your battery to the devices. DC/DC convertors with a short lead to the devices will negate this and supply the stated voltage to the device.

Derek

[Vox45]

To protect your devices you could use the DC/DC convertors. But you will need enough power capability to power each device possibly at different voltages. Sounds odd but manufacturers all claim 12 volt. But if you read their blurb some say 12 volt others state that their devices work from 11 volts up to 14 volts (as in EQ8). QSI state that their cameras work between 12 volts and 14 volts but alarm, (actually mine shuts down) if above 14 volts. Have a read of this thread,

http://stargazerslounge.com/topic/46532-a-reminder-about-charging-your-powertanks/

second to last post in particular. I tried to explain it  there.

Small DC/DC convertors just have not got the power capabilities. Don't forget that the more power your devices take the bigger the voltage drop in the line from your battery to the devices. DC/DC convertors with a short lead to the devices will negate this and supply the stated voltage to the device.

Derek

Interesting read indeed ! So something like this would be a good addition ? It's really a 12V regulator I need then, not a convertor ?

[Vox45]

I did something similar with mine, DC-DC convertors are a good idea if you want to power multiple I tems (usb, camera, 6v mount) I can either use mine with a 12v battery or a 6A mains adaptor in the house and fed outside.

Alan

So you added a regulator for each connection correct ?

[Physopto]

Interesting read indeed ! So something like this would be a good addition ? It's really a 12V regulator I need then, not a convertor ?

Hi,

Yes I have added several convertor/regulators. But the one you showed here is very expensive. Give me a short time and I will post the ones I bought.

Derek

[Vox45]

Hi,

Yes I have added several convertor/regulators. But the one you showed here is very expensive. Give me a short time and I will post the ones I bought.

Derek

OMG ! I misread the price at 8.99$ not 89$

[Alien 13]

So you added a regulator for each connection correct ?

Yes in my case I needed 6v for the mount 7.5v for the DSLR and a 5v to run my phone (used as an intervalometer) if your kit is all 12-13.6v then fused outputs should suffice.

The DC-DC convertors I used are rated at 3A and got 10 for about £8

Alan

[Vox45]

It would power the mount (HEQ5, not sure about the current) my Canon DSLR with the Astronomiser battery kit (12v to 30v 1.5A) and my powered hub (12V, 2.5A)

So in your mind, a regulator would not be needed ?

[Physopto]

Hi,

Here is the Web site:

http://www.hunterfield.co.uk/epages/es136853.sf/en_GB/?ObjectPath=/Shops/es136853/Products/TL060F_4Pin

It is rated at 60Watts  and 12.2 volts out regulated, i.e. 5 amps. I think if memory serves me right is 10 to 30 volt input. I think these will power almost any of our needs and with some headroom.

Anyway it is my answer to wrecking gear inadvertently when things go wrong as they often do out in the field. I can't afford a blown QSI camera at £3000. Don't forget if you use a charger they can go up to 14.4 volts ( I use my gear at Star Parties) and that is often beyond  your equipment specs. If a NEQ6 or EQ8 voltage drops below 11 volts at the mount because of line voltage drop it can easily blow the control board, there is a warning about that somewhere.

Derek

[Vox45]

ah so close ! I need 6 amps

But I see what you mean. A bit easier as I am not good at soldering and such. I'll look into all this, maybe even try my luck at the DC-DC convertors shown above if I can muster enough courage