Voltage drops off when doing full-throttle?

Batteries, Chargers, and Battery Management Systems.
Post Reply
User avatar
Marv1337n   1 W

1 W
Posts: 55
Joined: Jul 07 2018 5:16am
Location: Germany

Voltage drops off when doing full-throttle?

Post by Marv1337n » Jul 22 2018 5:43am

So I've recently got a watt meter to monitor the power usuage of my eBike and I've noticed something.
When I'm going full-throttle the voltage drops off from like 54v to 48v whilst the motor is getting around 1400-1500w power.
Is that something to worry about? The battery pack is made with Panasonic PF cells which I haven't heard too much bad about, so anyone got an idea?

elmannen   10 mW

10 mW
Posts: 27
Joined: Jun 26 2012 5:25pm
Location: Sweden

Re: Voltage drops off when doing full-throttle?

Post by elmannen » Jul 22 2018 7:03am

How many cells in paralell do you have ?

User avatar
Marv1337n   1 W

1 W
Posts: 55
Joined: Jul 07 2018 5:16am
Location: Germany

Re: Voltage drops off when doing full-throttle?

Post by Marv1337n » Jul 22 2018 7:47am

elmannen wrote:
Jul 22 2018 7:03am
How many cells in paralell do you have ?
5 with a total capacity of 13.6ah

brone   10 mW

10 mW
Posts: 25
Joined: Jun 26 2018 2:45pm

Re: Voltage drops off when doing full-throttle?

Post by brone » Jul 22 2018 8:07am

5P of PF cells are 2.9Ah * 5 = 14.5Ah. I have 4P of PF cells and don't have this kind of drop. It's usually 3-4V max when romping. Either your cells are old or not genuine

User avatar
Marv1337n   1 W

1 W
Posts: 55
Joined: Jul 07 2018 5:16am
Location: Germany

Re: Voltage drops off when doing full-throttle?

Post by Marv1337n » Jul 22 2018 8:22am

brone wrote:
Jul 22 2018 8:07am
5P of PF cells are 2.9Ah * 5 = 14.5Ah. I have 4P of PF cells and don't have this kind of drop. It's usually 3-4V max when romping. Either your cells are old or not genuine
Well I was going with the minimum capacity which is 2.7Ah * 5 = 13,5Ah. Going with the max. capacity is a bit too optimistic for me. Well it could be only a drop of 3-4V I'm not entirely sure but there is a drop for you too?

brone   10 mW

10 mW
Posts: 25
Joined: Jun 26 2018 2:45pm

Re: Voltage drops off when doing full-throttle?

Post by brone » Jul 22 2018 8:24am

Marv1337n wrote:
Jul 22 2018 8:22am
brone wrote:
Jul 22 2018 8:07am
5P of PF cells are 2.9Ah * 5 = 14.5Ah. I have 4P of PF cells and don't have this kind of drop. It's usually 3-4V max when romping. Either your cells are old or not genuine
Well I was going with the minimum capacity which is 2.7Ah * 5 = 13,5Ah. Going with the max. capacity is a bit too optimistic for me. Well it could be only a drop of 3-4V I'm not entirely sure but there is a drop for you too?
Of cource, every cell has a voltage drop off. If you want less drop off buy high-current cells like the Samsung 25R or LG HG2

User avatar
Marv1337n   1 W

1 W
Posts: 55
Joined: Jul 07 2018 5:16am
Location: Germany

Re: Voltage drops off when doing full-throttle?

Post by Marv1337n » Jul 22 2018 8:25am

brone wrote:
Jul 22 2018 8:24am
Marv1337n wrote:
Jul 22 2018 8:22am
brone wrote:
Jul 22 2018 8:07am
5P of PF cells are 2.9Ah * 5 = 14.5Ah. I have 4P of PF cells and don't have this kind of drop. It's usually 3-4V max when romping. Either your cells are old or not genuine
Well I was going with the minimum capacity which is 2.7Ah * 5 = 13,5Ah. Going with the max. capacity is a bit too optimistic for me. Well it could be only a drop of 3-4V I'm not entirely sure but there is a drop for you too?
Of cource, every cell has a voltage drop off. If you want less drop off buy high-current cells like the Samsung 25R or LG HG2
Oh I wasn't aware of that and I've thought that would be a sign that my BMS is damaged or something like that.

Jon NCal   1 kW

1 kW
Posts: 369
Joined: Jun 15 2015 3:59pm
Location: Mendocino, California

Re: Voltage drops off when doing full-throttle?

Post by Jon NCal » Jul 22 2018 8:26am

brone wrote:
Jul 22 2018 8:07am
5P of PF cells are 2.9Ah * 5 = 14.5Ah. I have 4P of PF cells and don't have this kind of drop. It's usually 3-4V max when romping. Either your cells are old or not genuine
Is that 3-4 volt drop at 1400-1500w?

brone   10 mW

10 mW
Posts: 25
Joined: Jun 26 2018 2:45pm

Re: Voltage drops off when doing full-throttle?

Post by brone » Jul 22 2018 8:28am

Jon NCal wrote:
Jul 22 2018 8:26am
brone wrote:
Jul 22 2018 8:07am
5P of PF cells are 2.9Ah * 5 = 14.5Ah. I have 4P of PF cells and don't have this kind of drop. It's usually 3-4V max when romping. Either your cells are old or not genuine
Is that 3-4 volt drop at 1400-1500w?
Yes. BBS02 58V @ 25A

User avatar
flippy   1 MW

1 MW
Posts: 1669
Joined: Aug 12 2015 3:07pm

Re: Voltage drops off when doing full-throttle?

Post by flippy » Jul 23 2018 1:34pm

Seems normal considering you are killing those poor pannies.

You need a much bigger battery (more P) in order to handle the current.
Lithium beats liquid dinosaurs.

Post Reply