Efuel High Power Charging Questions

[hedge]

I've posted this on my club site as well so apologise to those that have access to both, I really want a broad set of eyes and replies...

I am parallel charging 6 x 5000mah 6s packs.

Now I am not interested in theory, not being rude here just not after maths proving I can charge at X rate. To justify that statement, in theory I should not have blown up my old PL8 (charging at 12v - 60a) but I did and in theory I should be able to charge at 30v and 50a but the manufacturers of the Efuel PSU put a note in the box especially for PL8 users saying set the PL8 to max 24v and max 40a.

Soooo.... Before I blow up another PL8... If anyone is using this PSU do I set it to run at 30v? And do you have any other recommendations?

1) I have read that I need to power on the PSU and wait 15secs before connecting the charger so will follow that route
2) The PSU had a pull out for the PL8 saying to set the PL8 to accept a max voltage 24v and max current 40a which I have done.

Last question is everyone just using the user pre-set "high power" or direct amp charging, rather than setting to be C charge i.e. set to 5A per pack rather than let it decide based on C rating ie 1C?

Thanks

[Mark_T]

Well, in theory and in practice, yes, 12V 60A should have blown up your PL8 as it beyond it's rating at 12V

Also no, 50A at 30V is also outside the spec for the PL8.

Your limit is around 1344W @ +26.35V so setting for 24V and 40A is safely inside that limit.

Yes, use the high power setting, the 'C' option tends to be more cautious and will charge slower in most cases.

[hedge]

Well, in theory and in practice, yes, 12V 60A should have blown up your PL8 as it beyond it's rating at 12V

Also no, 50A at 30V is also outside the spec for the PL8.

First of all thank you very much for replying... and now I will break my rule on post #3 But hey its my rule lol

The specs for the pl8 say...

Power conversion:Synchronous DC/DC converter, supports multiple switcher frequencies of 31.25 kHz, 62.5 kHz, 125 kHz; user selectable by preset, 85% to 93% efficiency depending on output current
Continuous max output power: 612W @ +12VDC input, 1344W @ +26.35VDC

So I take from this

60a * 12v = 720w * 85% efficiency = 612w

[Grumpy]

The PL8 is ok for input voltage up to 32V, so you will be fine as far as the PL8 is concerned to set the PSU to 30V.

The problem isn't with the PL8 it is with the Efuel PSU. The PSU has 1200W rating but the PL8 has a maximum of 1344W, so if you were maxing out your PL8 then you would exceed the rating of the PSU and possibly damage it. I'm guessing that's why you get the instructions with the PSU, i.e. to set the PL8 so that it cannot exceed the rating of the PSU. This is to protect the PSU, not the PL8.

I dont know why your PL8 failed but it certainly wasn't because the PSU was supplying to high a voltage or too many amps.

[Grumpy]

Well, in theory and in practice, yes, 12V 60A should have blown up your PL8 as it beyond it's rating at 12V

Also no, 50A at 30V is also outside the spec for the PL8.

Actually 12v x 60A is within the PL8 rating, 60A is actually the upper limit on input current.

30V x 50A would be over the power limit of the PL8 but the Efuel PSU cannot supply that much power anyway, it's limit is 1200W so at 30V the most current it could supply is 40A. The PSU would trip (or burn) if the PL8 demanded more.

[hedge]

The PL8 is ok for input voltage up to 32V, so you will be fine as far as the PL8 is concerned to set the PSU to 30V.

The problem isn't with the PL8 it is with the Efuel PSU. The PSU has 1200W rating but the PL8 has a maximum of 1344W, so if you were maxing out your PL8 then you would exceed the rating of the PSU and possibly damage it. I'm guessing that's why you get the instructions with the PSU, i.e. to set the PL8 so that it cannot exceed the rating of the PSU. This is to protect the PSU, not the PL8.

I dont know why your PL8 failed but it certainly wasn't because the PSU was supplying to high a voltage or too many amps.

I agree with all you say - on paper - just the experience I had was horrid. If the pl8 had blown in the house It would have been a complete carpet, upholstery and curtain clean/replacement. The smell was horrid and toxic. My mate at the flying field smelt it (it stank) cause one of my battery boxes in my car boot was near the PL8 when it blew!!! Thank fully the man cave has now recovered to its normal smell of O'd Nitro

[Grumpy]

So I take from this

60a * 12v = 720w * 85% efficiency = 612w

Yes, that's correct, but as a general rule with adjustable voltage power supplies you should set the voltage as high as it can go within the rating of the charger. In this case 30V would be fine for your PL8 but you would need to limit the PL8 to 40A input to prevent it from exceeding the 1200W rating of the Efuel supply... I guess Efuel say 24V to give a little headroom on their rating, they don't appear very confident that their 1200W PSU can really deliver 1200W!

[Grumpy]

I agree with all you say - on paper - just the experience I had was horrid. If the pl8 had blown in the house It would have been a complete carpet, upholstery and curtain clean/replacement. The smell was horrid and toxic. My mate at the flying field smelt it (it stank) cause one of my battery boxes in my car boot was near the PL8 when it blew!!! Thank fully the man cave has now recovered to its normal smell of O'd Nitro

Like I said i cant explain why that happened but it wasn't because the PSU exceeded any rating of the PL8, because the PL8 exceeds or matches the rating of that PSU in all areas. Also bear in mind that the PL8 will only draw the current it needs, just because the supply is rated at 60A does not mean that the PL8 will always draw 60A.

[hedge]

And likewise the PL8 does not seem capable of achieving its full potential or protecting itself as mine was set not to exceed input 12v 60A but it appears it did and it fried. That said there was a no questions asked RMA BUT I don't want to do it again - if I can help it. So rather than paper based discussions which you and I can happily do all day, I am after what people using the two are setting them at in the real world.

[Mark_T]

Actually 12v x 60A is within the PL8 rating, 60A is actually the upper limit on input current.

60A is the maximum current, but it can't handle the Watts at the lower voltage.

If you manage to pull 60A out of it at 12V it will be outside the spec.

The eFuel PSU is 85-93% efficient apparently, and we know that is only an estimate, not a hard limit, so it only has to be closer to 93 than 85 which is not unlikely under a heavy load and it can feed the PL8 more than it can cope with.

All comes down to what you are actually managing to pull out, but 6x6S 5000 at 1C would do it ...

Edit: corrected typo.

[Grumpy]

60A is the maximum current, but it can't handle the Watts at the lower voltage.

If you manage to pull 60A out of it at 12V it will be outside the spec.

That's within the spec of the PL8 but exceeds the 50A rating of the Efuel PSU.. as i said, it's the PSU that is the 'weak link'. The failure of the PL8 was nothing to do with exceeding it's limits that's for sure. The PL8 cant exceed it's limits anyway, it just goes to it's max and stops.

Sometimes chargers do fail, it's not necessarily because of the pSU.

[scallybert]

Maybe misreading what people are saying, but I find it hard to believe that a PL8 would draw a current from a PSU that the PL8 would know exceeded its [PL8's] ratings. It measures the input V & I. It knows these things... It measure everything... Continuously...

My understanding is that the input current limit is purely to protect the PSU. Ie to stop the PL8 drawing more current than the PSU can safely supply.

[Grumpy]

My understanding is that the input current limit is purely to protect the PSU. Ie to stop the PL8 drawing more current than the PSU can safely supply.

100% correct, that's what i was trying to say. That is why the instructions for the Efuel PSU mention setting current limits in the PL8 software. not for charger protection but for PSU protection.

[Mark_T]

That's within the spec of the PL8 but exceeds the 50A rating of the Efuel PSU..

You are right of course, I forgot to check the PSU after reading the 60A 12V comment in the first post.

Only thing I can think of is if the PSU output became unstable it could cause issues for the PL8 but they usually just shut down in that situation.

[Mike656]

Also looking at the Revolectric site, while the PL8 has a max input current of 60 amps, it has a max output current of 40 amps. So anything more than 4 x 5000mah packs at 2C could take it over its limit (hopefully the software prevents this). If I was charging 6 x 5000mah packs, I personally wouldn't charge over 1C. That way, the psu wouldn't be running at full capacity either.