[PSUBS-MAILIST] 36vdc charger

Thu Mar 29 11:06:29 EDT 2018

Just to add to that, if you must run multiple batteries in series, both to draw from and to charge, then do as I suggested and use bus bars if you can, but you will also want to assess each battery or cell on an individual basis more often as part of your preventative maintenance. If one cell starts to drop voltage out of line with the rest, you will want to replace it early to prolong the life of the others. If you let one get really bad, it can adversely affect the others in the string over multiple charge cycles. That said, unless you are purchasing single cells specifically, most off the shelf batteries that you buy are essentially series combinations of multiple cells anyway, and when a battery goes bad, it is likely only one or two of the internal cells that have actually degraded. The intimate nature of the plate or wound construction of cells integral to a single battery minimizes the problems, and there are also economies of scale at work. Rarely can you even measure individual cell voltages in an off-the-shelf battery. Stringing multiple batteries together in series is fundamentally no different, but if you are able to monitor individual cell voltages (those of you with electronic controls / PLCs) as a measure of cell / battery health, you can get an early warning of an impending failure within your string.

Sean

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-------- Original Message --------
On Mar 29, 2018, 08:46, Jon Wallace via Personal_Submersibles wrote:

> Thanks for those details Sean.
>
> ---------------------------------------------------------------
> From: Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org>
> To: personal_submersibles at psubs.org
> Sent: Wednesday, March 28, 2018 10:41 PM
> Subject: Re: [PSUBS-MAILIST] 36vdc charger
>
> The issue with charging multiple cells in series is that small variances in internal resistance of each cell can lead to cell imbalance over time. This also happens to some extent in parallel configurations, but at least then you are controlling the charge voltage across the cell. If you have a sophisticated battery management system which can isolate or switch charge voltage to individual cells, you can significantly extend the working life of the battery, but it may be cheaper just to replace batteries more often. I might give some consideration to high current capability switches to isolate and charge cells independently in the absence of a BMS. If I were constrained to a series battery configuration, I would do all I could to eliminate any resistance between them, such as using large bus bars instead of cables.
>
> Sean
>
> -------- Original Message --------
> On Mar 28, 2018, 14:12, hank pronk via Personal_Submersibles < personal_submersibles at psubs.org> wrote:
>
>>
>
> Jon,
> I had a 36V system for a season but am back to two 24V banks, but I always charge 12V at a time.  It is also easier to find a charger for AGM in 12 or 24V.   Sean mentioned one time to charge individual batteries instead of a group and I have followed that advice.
> Hank
>
> On Wednesday, March 28, 2018, 1:38:34 PM MDT, Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
> For those with 36v systems, what charger are you using?  How many amps?  How long to charge the bank of batteries?
>
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