T-Pain Is On A Boat: Re: [Electric Boats] Charging batteries in series?

Friday, January 16, 2015

Re: [Electric Boats] Charging batteries in series?

Having just worked on the software drivers for a "SBS" (smart battery system) I can tell you that modern (LiFePO et al) battery packs contain electronics that are designed to instruct their own individual (per pack) charger on what to deliver for optimum charging.

They use SMBus for communicating (a variety of I2C) that is used in automobiles etc.

This is why modern battery packs ought to charged individually especially for the "topping up" as you call it.

On Fri, Jan 16, 2015 at 11:12 AM, 'Capt. Mike' biankablog@verizon.net [electricboats] <electricboats@yahoogroups.com> wrote:

John

I believe it would have. John. Though I leave it to the battery experts here to explain why. I started out with a 48 volt series charger like you. Then added a Dual Pro 4 charger into the mix that charges each battery individually. At anchor I use the series charger for the bulk charge then switch to the Dual Pro for the finishing charge. If I'm at the dock and have grid power available I'll use the Dual Pro for the full charge. This Helps keep the batteries in better balance from my voltage observations.

Capt. Mike
Sent from on board BIANKA
http://biankablog.blogspot.com
From: "John Acord jcacord@gmail.com [electricboats]" <electricboats@yahoogroups.com>
Sender: electricboats@yahoogroups.com
Date: Fri, 16 Jan 2015 06:54:39 -0800
To: <electricboats@yahoogroups.com>
ReplyTo: electricboats@yahoogroups.com
Subject: [Electric Boats] Charging batteries in series?

For years I have used flooded cells in series/parallel circuit and never noticed this. Having completed the motor installation in my boat I have just received my set of four 12V AGM 100 AH batteries and charger, Lifeline batteries and Qui-Q 48V charger with temperature compensation.

Off the truck the individual batteries terminal voltages varied by about 60 mV, not unexpected. I put each through a short discharge cycle and then wired up in series to charge them. At the start of the charging cycle I noticed quite a variation in terminal voltage of each battery which I expected. What I did not expect was that as the current tapered off, less than three amps, the differences in voltage between individual batteries increased quite noticeably. I would have expected that each battery would have accepted the charge it needed and the voltages would have become close to the same for each battery.

Would it have been better to charge each battery individually before putting them into series?

After putting the battery stack through a few cycles should the difference in battery voltages go away?

Any thoughts?

thanks,
John Acord

--
Flatwater Electronics
www.flatwaterfarm.com
"Neurosurgery for computer looms."