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Discussion Starter #1
PS, how about replacing all the 32 fuses with wores and have a middle 200A pack fuse?



From: [email protected]
To: [email protected]
Subject: Parallel Fuses? LiFePO4 Buddy balancing
Date: Wed, 29 Sep 2010 08:18:17 -0400




Hi,

In my www.evalbum.com/2749 E-Cat I'm thinking of putting a larger Etek-RT 2k rpm @ 48V motor on a Johnson 9.9hp outboard with a 16x16 prop instead of the 8x8 Briggs outboard using 80A. So my current will be in the 120 - 140A range and I have the Lee Hart recommended 60A dual buddy pair fuses on the Thundersky 100ah batteries (to make 200ah pairs). I have 32 fuses for the 32 cells in parallel pairs to make 16 x 3.3 = 52.8V @ 200ah total. So I essentially have 120A worth of fusing and now need to bump them up for a larger motor/prop. I have a clump of 60A fuses and was thinking of doubling them up, another 32 60A fuses for 240A worth of fusing. I know generally you don't want to parallel fuses but not sure why it wouldn't work in this situation, if one fuse starts getting hot, increasing resistance, its' buddy will start to see more current flow and balance? I know RayChem with PTC's says you can parallel their PTC's which sounds like a similar application.

Have a renewable energy day,
Mark
www.reevadiy.org

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Registered
Joined
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70 Posts
Discussion Starter #2
There are many solutions, some seem more reliable than others especially in
a marine environment, any fuse holder with a slight amount of corrosion may
blow the paralleled fuse followed immediately by itself. Batteries behave
much better in series, so why not put all in a single series string,
(Systems generally are better with more voltage and somewhat less current
and besides) the controller translates the power efficiently into pulses and
the motor inductance and the Diodes in the controller give a higher current
in the motor than the batteries need to supply, and you would only need one
fuse, The batteries are much more reliable in one series string, the only
drawback is needing a higher voltage charger,or charge half the pack at a
time but be careful to maintain balance.
Regards,
*Dennis Lee Miles* (Director) *E.V.T.I. inc*.
*www.E-V-T-I-Inc.COM <http://www.e-v-t-i-inc.com/> *(Adviser)*
EVTI-EVAEducation Chapter
*
Phone (863) 944 - 9913
Initial demand (computed by extrapolating the reservations for GM Volt and
Nissan Leaf,) shall exceed 200,000 vehicles in 2010 and 2011. However only
50,000 vehicles will be marketed, so a LARGE demand for Nice Newer
Conversions is predicted!
==================================================================

Mark Hanson <[email protected]>wrote:

>
> PS, how about replacing all the 32 fuses with wires and have a middle 200A
> pack fuse?
>
>
>
> From: [email protected]
> To: [email protected]
> Subject: Parallel Fuses? LiFePO4 Buddy balancing
> Date: Wed, 29 Sep 2010 08:18:17 -0400
>
>
>
>
> Hi,
>
> In my www.evalbum.com/2749 E-Cat I'm thinking of putting a larger Etek-RT
> 2k rpm @ 48V motor on a Johnson 9.9hp outboard with a 16x16 prop instead of
> the 8x8 Briggs outboard using 80A. So my current will be in the 120 - 140A
> range and I have the Lee Hart recommended 60A dual buddy pair fuses on the
> Thundersky 100ah batteries (to make 200ah pairs). I have 32 fuses for the
> 32 cells in parallel pairs to make 16 x 3.3 = 52.8V @ 200ah total. So I
> essentially have 120A worth of fusing and now need to bump them up for a
> larger motor/prop. I have a clump of 60A fuses and was thinking of doubling
> them up, another 32 60A fuses for 240A worth of fusing. I know generally
> you don't want to parallel fuses but not sure why it wouldn't work in this
> situation, if one fuse starts getting hot, increasing resistance, its' buddy
> will start to see more current flow and balance? I know RayChem with PTC's
> says you can parallel their PTC's which sounds like a similar application.
>
> Have a renewable energy day,
> Mark
> www.reevadiy.org
>
> --------------
>



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