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Old Jan 16, 2012, 07:02 PM
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United Kingdom, London
Joined Dec 2003
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Quote:
Originally Posted by Tim Marks View Post
Hi:

Good question. The MPA will limit the flow of current on the balance wires to 1A, but as soon as you connect the main pack leads together, the current flow is only limited by the internal resistance of the batteries (which is very low, and varies from chemistry-to-chemistry). There is no other protection, thermal fuse or otherwise on your main pack leads. Current always chooses the path of least resistance.

So this is why the MPA will protect all of the balance wires, and your main pack wires will always be able to handle many times the current surge while the paralleled packs equalize. So the only remaining question is, how well can your LiPos tolerate, e.g., 5C or 10C charge for 1-3 minutes. I think most good quality LiPo these days won't break a sweat on it. So it's likely peoples' concern over this topic is over-stated, IMO.

Tim Marks
Thanks once again, then going by this you could just only connect the balance wires for the 1st few minutes let the cells do most the equalising then connect the main leads..

Although as you say most modern batteries wouldn't have a problem with that C rating anyway.
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Old Jan 16, 2012, 07:15 PM
President, FMA, Inc.
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Quote:
Originally Posted by topgearuk View Post
Thanks once again, then going by this you could just only connect the balance wires for the 1st few minutes let the cells do most the equalising then connect the main leads..

Although as you say most modern batteries wouldn't have a problem with that C rating anyway.
Hi:

I guess theoretically this could work; however, if the state of charge between the packs were substantially high, the thermal fuses and indicators might scream. It's probably not best practice to utilize the hardware for this purpose. The thermal fuses and indicators are there to protect against incorrect connections, not really intended as a tool for precise regulatation of charging current. Before I could even recommend this, I'd have to see some statistical analysis of the tolerance of the thermal fuses. In doing what you say, it may be possible to end up actually de-balancing the pack(s), but I can't be sure.

Tim Marks
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Old Jan 16, 2012, 07:16 PM
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USA, GA, Marietta
Joined Aug 2005
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Quote:
Originally Posted by topgearuk View Post
Thanks once again, then going by this you could just only connect the balance wires for the 1st few minutes let the cells do most the equalising then connect the main leads..

Although as you say most modern batteries wouldn't have a problem with that C rating anyway.
I think is is just the other way around. Connecting the balance wires when the packs are very mismatched would result in an attempted high current. However the poly fuses would go to high resistance and stop the current flow. Therefore the cells would not self balance.

So to get two mismatched packs to balance you sould have to connect the main charge/discharge leads.

Have I got that right Tim?

Glen
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Old Jan 16, 2012, 07:23 PM
President, FMA, Inc.
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Originally Posted by ggcrandall1 View Post
I think is is just the other way around. Connecting the balance wires when the packs are very mismatched would result in an attempted high current. However the poly fuses would go to high resistance and stop the current flow. Therefore the cells would not self balance.

So to get two mismatched packs to balance you sould have to connect the main charge/discharge leads.

Have I got that right Tim?

Glen
Hi Glen:

For the most part, you are correct. But I think the characteristics of the thermal fuses is to increase resistance to the point where they'll pass up to 1A of current. Even if they don't pass a full 1A, they likely allow some current to pass. So I think, given enough time, the packs might, more-or-less equalize; however, the bigger concern that I've tried to point out is that, if one thermal fuse passes 1A and another passes .9A, you might have a situation where the pack becomes out of balance the more time passes.

In either case, it would require more research before I could draw a conclusion. I respectfully request that you guys don't ask me to run those tests to find out!

Tim Marks
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Old Jan 16, 2012, 08:04 PM
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To be honest, 1A current should be fine for cells at least ~300mAHr or larger, and 3C capable.

Just don't connect the main leads, at least for some time. I guess it is useful to check the pack with some type of battery monitor first.

However I don't think this should be a normal type of use, to attach packs in way different charge states. IMHO of course.

BTW, I really like my new PowerLab 6!

I will probably add the MPA eventually. Already have two of the safe parallel adapter boards (actually 4 - 2 in each of two "flavors"). However I am trying to see where my main charging is going to lead me, since it will determine the flavor of MPA balancing connection I will need to choose.
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Last edited by Alan Hahn; Jan 16, 2012 at 08:13 PM.
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Old Jan 17, 2012, 12:59 PM
President, FMA, Inc.
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Originally Posted by Alan Hahn View Post
To be honest, 1A current should be fine for cells at least ~300mAHr or larger, and 3C capable.

Just don't connect the main leads, at least for some time. I guess it is useful to check the pack with some type of battery monitor first.

However I don't think this should be a normal type of use, to attach packs in way different charge states. IMHO of course.

BTW, I really like my new PowerLab 6!

I will probably add the MPA eventually. Already have two of the safe parallel adapter boards (actually 4 - 2 in each of two "flavors"). However I am trying to see where my main charging is going to lead me, since it will determine the flavor of MPA balancing connection I will need to choose.
Hi:

It might make your job easier when you realize there is only one version of the MPA currently, and that's for XH connectors. Whether or not we'll support other balance connectors down the road, I can't say at present.

Tim Marks
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Old Jan 17, 2012, 02:50 PM
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Originally Posted by Tim Marks View Post
Hi:

It might make your job easier when you realize there is only one version of the MPA currently, and that's for XH connectors. Whether or not we'll support other balance connectors down the road, I can't say at present.

Tim Marks
Fortunately I think that's what my biggest cells have. For my smaller packs (4s and lower, with cells <3000mAHr) I could just use my Safe Parallel Adapter boards, of which I have 2 varieties. I couple that with adapter boards that I used on my old FMA 4s chargers, and I think I have everything covered.

To be honest, it has been difficult keeping track of all these balancing connectors. I think I have packs that have used almost every variety (TP, Hyperion, HK, Revolectrix). Still have one older pack that I could never figure out!
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Old Jan 17, 2012, 04:39 PM
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For you guys that have the Cellpro 10XP charger and use the MPA, only connect the pigtail that has the black ground wire to channel 1 for 2S - 5S cell count packs. If you have 6S - 8S packs, then you will connect both pigtails to the charger. Connecting both pigtails to the charger when you have a 2S - 5S pack connected will give you a Bad S. Count error. Please let me know if you have any questions, thanks.
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Old Jan 17, 2012, 06:35 PM
Tombsy
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Canada, AB, Calgary
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My MPA arrived today, it's a beast it looks bigger in person .
It fits in my charger box perfectly though, nice work Thanks Tim
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Old Jan 18, 2012, 02:15 PM
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MPA User Guide:

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http://revolectrix.com/support_docs/item_1400.pdf
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Old Jan 28, 2012, 09:47 AM
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United States, WY, Cheyenne
Joined Aug 2004
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Quote:
Originally Posted by Tim Marks View Post
Hi:

We're looking at supplying adapters from Deans Ultra to EC3 soon. Perhaps we can also look into other adapters. Coming off the PCB with bare wires would kind of be ugly and dangerous I think?

Tim Marks
I love my 4 CellPros and I will wait for the Deans Ultra to EC3 adapters.
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Old Jan 30, 2012, 08:57 AM
Learnin mo ever day
United States, NJ, Tinton Falls
Joined Jul 2007
139 Posts
I want to extend the length of the cable between the MPA and my PL8. Is there an off the shelf cable, or should I just splice in some 22ga wire on each lead? I need a total of about 3 feet.
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Old Jan 30, 2012, 09:42 AM
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Originally Posted by wjbender View Post
I want to extend the length of the cable between the MPA and my PL8. Is there an off the shelf cable, or should I just splice in some 22ga wire on each lead? I need a total of about 3 feet.
Hi,

We currently do not offer a longer cable.
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Old Jan 30, 2012, 12:11 PM
Learnin mo ever day
United States, NJ, Tinton Falls
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Originally Posted by Howard Matos View Post
Hi,

We currently do not offer a longer cable.
A total length of 3' will not cause a problem, correct?
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Old Jan 30, 2012, 04:19 PM
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United States, FL, Gainesville
Joined Nov 2006
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FYI - Finally got a full day of charging with my PL8 and MPA setup. WOW, I mean WOW. Absolutely one of my smartest purchases ever in this hobby. I thought the PL8 was, but this just ices the cake.
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