Rechargeable Power Supplies & Battery Life: A Buyer’s Guide

[AJ567]

Rechargeable Power Supplies & Battery Life: A Buyer’s Guide

Rechargeable power supplies can offer superior noise performance and great convenience. A key concern for anyone considering this type of power supply is battery life… and on this issue, unfortunately, there’s a lot of misinformation and marketing nonsense out there. I’ve recently been down a rabbit hole trying to understand the complexities of rechargeable battery capacity so I thought I’d share some learnings. 

I don’t claim to be an expert, just an interested consumer. Very happy for anyone reading this to correct me if necessary!

 

Capacity ratings… often not what they seem

Most brands state battery capacity in mAh, leading consumers to think (quite understandably) that they can divide the stated capacity by their current needs to get expected battery life, i.e. 20,000 mAh = 20 hours play time at 1A. This is not the case. The stated mAh capacity is usually in reference to the internal cell voltage, which is a lot lower than the 9v output voltage you will be using. So it’s a bit of a marketing trick to make capacity look bigger. Confounding the issue, the internal cell voltage varies by manufacturer. This is normally 3.7 or 7.4V; a minority of brands appear to state mAh capacity at 9v output, to be helpful to musicians… kudos. Additionally, you will never see the full capacity discharged due to inefficiencies (heat etc.) Good quality lithium batteries appear to have efficiency of about 85% overall.  

TLDR: below are estimates for the battery life you can expect for various products. The figures stated are the number of hours run time for a current draw of 1A @9v.

To get estimated battery life for your setup, divide the 1A estimate by the total current draw of your pedals in Amps (i.e. using a Volto 3 to power 450ma worth of pedals, I would expect to get 2.2 / 0.450 = 4.8 hrs)

NB not all of these supplies can actually supply a full 1A.

If anyone is actually interested in the details behind these estimates, let me know and I can fill you in on the research and calcs I have applied.

 

If you need isolated outputs, here are some options

1. Use a mission 529i or 529 and whatever USB battery pack you want.
Great solution, not cheap though.

2. Use any standard USB battery pack, plus as many Joyo ZGP-W adapters as you need.
Potentially a good, cost effective way of doing things. The Joyo ZGP-Ws are nifty devices that boost 5V USB voltage to 9V, as well as providing isolation and filtering. However, you need to bear in mind the current ratings. Each Joyo can supply a max of 400mA at 9V. The Joyo’s themselves are pretty inefficient (c.59%) and of course you need to draw more current at 5V than is supplied at 9V – the current load at the USB port will be roughly triple what your pedals draw at 9v. So, a standard 2.4A USB port can support 2 Joyo ZGP-Ws at full load. 

3. Use any of the single output products on the list above (e.g. Volto 3, Rockboard, Palmer) and add isolation adapters as necessary.
GigRig Isolators work well in this context. Each Isolator provides 4 isolated outs with 135mA capacity each. Joyo ZGP-W (400mA capacity) or ZGP (800mA capacity, operates only at 9V) will also work. However, bear in mind that the circuitry needed to provide isolation will also drain some current, and therefore reduce battery life:

• GigRig Isolators draw about 100mA by themselves
• Joyo ZGP-W has c.59% efficiency, so using one fully loaded at 400mA will cost you almost 300mA (at 9V).
• Joyo ZGP uses between c.50ma and c.200ma depending on the overall load (very small draw from pedals will cost you an additional 50mA, close to 800mA draw will cost you 200ma) 

4. Wait for the Harley Benton Powerbank+ and use it to power a multi-output Harley Benton or Strymon power supply.
The Powerbank+ appears to be an interesting forthcoming product. Massive battery capacity, and selectable output voltage at 9, 12, 18 or 24V. So, you can use it as a regular 9v power bank, or you can use it at 12V to power a Harley Benton ISO-1, ISO-2, or ISO-5. This would give you whole lot of isolated, mutli-voltage options. You could also use the Powerbank+ to power one of the Strymon power supplies at 24V.

 

Hope this is all useful info to somebody!

  

Edited April 27, 2020 by AJ567

[jrixn1]

1 hour ago, AJ567 said:

To get estimated battery life for your setup, divide the 1A estimate by the total current draw of your pedals in Amps (i.e. using a Volto 3 to power 450ma worth of pedals, I would expect to get 2.2 / 0.450 = 4.8 hrs)  

Does it depend on the voltage of the pedals?

This is what I would do:
First calculate the capacity of your battery (capacity = charge X voltage).  The charge (in mAh) and voltage (in V) should be written on the back of the battery or in its manual.
e.g. capacity = 6600mAh X 3.7V = 24420mWh

Then add up the power each pedal uses (power = current X voltage);
e.g. pedal 1 is 250mA, 9V: power = 250mA X 9V = 2250mW
pedal 2 is 50mA, 18V: power = 50mA X 18V = 900mW
Add these together to get the total power: 2250mW + 900mW = 3150mW.

Then divide the capacity by the power:
e.g. 24420mWh / 3150mW = 7.75 hours

Having said that - in my case, I did all the calculations and concluded I would be fine. Nevertheless, my rechargable battery ran out of juice during a gig and I haven't dared use it since.

[AJ567]

57 minutes ago, jrixn1 said:

Does it depend on the voltage of the pedals?

This is what I would do:
First calculate the capacity of your battery (capacity = charge X voltage).  The charge (in mAh) and voltage (in V) should be written on the back of the battery or in its manual.
e.g. capacity = 6600mAh X 3.7V = 24420mWh

Then add up the power each pedal uses (power = current X voltage);
e.g. pedal 1 is 250mA, 9V: power = 250mA X 9V = 2250mW
pedal 2 is 50mA, 18V: power = 50mA X 18V = 900mW
Add these together to get the total power: 2250mW + 900mW = 3150mW.

Then divide the capacity by the power:
e.g. 24420mWh / 3150mW = 7.75 hours

Having said that - in my case, I did all the calculations and concluded I would be fine. Nevertheless, my rechargable battery ran out of juice during a gig and I haven't dared use it since.

Yes that's right, but you would also need to assume some loss due to battery ineffiency (maybe 15%) and possibly some additional loss when you convert from 9v to 18v for pedal 2, depending on how you are doing it. I assume you are using some sort of adapter to achieve the 18V step up. Not sure what loss that adapter introduces... in the end your battery life would probably be more like 6 - 6.5 hrs.

If you are able to measure the input and output current of your 18V adapter that could be very handy for future readers!

[jrixn1]

It was theoretical, having seen a supply like this one, which has 5V, 9V, 12V, and 18V outputs.

 

[AJ567]

Ah gotcha. I think it's fair to calculate 100ma @ 18V as equivalent to 200ma @ 9V for these purposes. I already assumed some loss in the Joyo JP05 estimate I have in the table above.

[adamg67]

I've got a Batpack 8000, but I don't have a way of measuring the current draw. Hmm, well, I suppose I have a multimeter and 9v power supply plugs of both genders, so I could make something, but only for spot checking it, so maybe not worth it. If I'm bored (I'm still working so not likely) I'll try it.

My initial scientific measurments for a minimal board (more of a fly rig really) with DG Vintage Microtubes Ultra, DG Hyper Luminal and a Peterson strobe tuner (doing nothing most of the time obvs): it lasts aaaages.  I'm curious anyway, so I'll run a timer when I'm using it and see what it will do with those pedals running at least.

[AJ567]

5 hours ago, adamg67 said:

I've got a Batpack 8000, but I don't have a way of measuring the current draw. Hmm, well, I suppose I have a multimeter and 9v power supply plugs of both genders, so I could make something, but only for spot checking it, so maybe not worth it. If I'm bored (I'm still working so not likely) I'll try it.

My initial scientific measurments for a minimal board (more of a fly rig really) with DG Vintage Microtubes Ultra, DG Hyper Luminal and a Peterson strobe tuner (doing nothing most of the time obvs): it lasts aaaages.  I'm curious anyway, so I'll run a timer when I'm using it and see what it will do with those pedals running at least.

The batpack 8000 certainly looks like a great product, definitley one of the best of its type out there. Battery life on a small board like yours ought to be enough that it's not a concern at all. Nice!

[AJ567]

Updated with details of Joyo ZGP, thanks to @Al Krow

[Al Krow]

3 minutes ago, AJ567 said:

Updated with details of Joyo ZGP, thanks to @Al Krow

Glad it arrived safely  I've had more than one experience of things getting lost in the post when not sent by "signed for" delivery, which given the current shut down of local Post Offices means it can be a bit of a lottery. 

[Rich]

I’ve noticed this rechargeable Varta thingy on Thomann, and was wondering if it could be used as a pedalboard supply? The implication seems to be that yes, it could, as the specs show the USB outputs rated as "5V / 3A, 9V / 2A, 12V 1.5A". Which is jolly good, but I can't see for the life of me how the desired output voltage is selected. Anybody got any ideas?

https://www.thomann.de/gb/varta_wireless_power_bank_10000.htm

Edited July 10, 2022 by Rich

[pete.young]

Seems unlikely - i think it's depending on the device being charged having enough smarts to know what charging voltage it requires.

 

Plus you have the challenge of finding a USB C to 2.1mm centre neg daisy chain.

[Rich]

Yes I thought it might be something like that. Ah well, it was a nice idea while it lasted. 
 

12 minutes ago, pete.young said:

Plus you have the challenge of finding a USB C to 2.1mm centre neg daisy chain.

This bit wouldn’t be a problem. There are USB to 2.1 centre pos cables available, 10 minutes with a soldering iron and some wire & plugs and hey presto it’s a centre neg daisy chain

[pete.young]

The key to this is USB-C PD - the PD bit stands for Power Delivery, it's a fast-charging technology which requires a USB-C PD enabled device such as a recent iPhone, Pixel phone or Samsung S20. Fascinating stuff.

 

https://www.belkin.com/uk/resource-center/power-delivery/

 

So can you get an effects pedal supply which supports USB-C PD, I hear you cry? Well apparently yes you can.  https://www.thomann.de/gb/mission_engineering_529_m_usb_pd_converter.htm . If you can wait for it to come back into stock.

 

Another option might be this powerbank https://www.thomann.de/gb/harley_benton_powerplant_powerbank.htm which has 2 9V DC -ve outputs, 1.2A which should be good for a handful of low-current pedals. Think I might go for one of those myself. Just realised this is one of the banks listed in the original post.

 

The Harley Benton Powerbank Plus is now discontinued so the OP's solutions using that are no longer viable.

Edited July 11, 2022 by pete.young

[Rich]

13 hours ago, pete.young said:

Another option might be this powerbank https://www.thomann.de/gb/harley_benton_powerplant_powerbank.htm which has 2 9V DC -ve outputs, 1.2A which should be good for a handful of low-current pedals. Think I might go for one of those myself.

Yes, I think this is probably the one to have. I was hoping the Varta would do a similar job for less ££, but it seems not. 

[AJ567]

On 11/07/2022 at 08:46, pete.young said:

The key to this is USB-C PD - the PD bit stands for Power Delivery, it's a fast-charging technology which requires a USB-C PD enabled device such as a recent iPhone, Pixel phone or Samsung S20. Fascinating stuff.

 

https://www.belkin.com/uk/resource-center/power-delivery/

 

So can you get an effects pedal supply which supports USB-C PD, I hear you cry? Well apparently yes you can.  https://www.thomann.de/gb/mission_engineering_529_m_usb_pd_converter.htm . If you can wait for it to come back into stock.

 

Another option might be this powerbank https://www.thomann.de/gb/harley_benton_powerplant_powerbank.htm which has 2 9V DC -ve outputs, 1.2A which should be good for a handful of low-current pedals. Think I might go for one of those myself. Just realised this is one of the banks listed in the original post.

 

The Harley Benton Powerbank Plus is now discontinued so the OP's solutions using that are no longer viable.

 

The Mission 529 (with any usb-c PD pack) works really well. That's what I'm using at the moment.